Microbiology Final Exam 100% VERIFIED ANSWERS 2024/2025 CORRECT, Exams of Nursing

Download Microbiology Final Exam 100% VERIFIED ANSWERS 2024/2025 CORRECT and more Exams Nursing in PDF only on Docsity! Microbiology Final Exam 100% VERIFIED ANSWERS 2024/2025 CORRECT Which of the following structures are found only in prokaryotic cells? A) endoplasmic reticulum B) peptidoglycan C) nucleolus D) lysosomes B Which of the following cellular structures can be found in both prokaryotic and eukaryotic cells? A) nucleus B) Golgi apparatus C) lysosomes D) ribosomes D Which is the correct ordering of cell wall components starting from outside the cell and going inward? A) In Gram-negative bacteria: peptidoglycan, lipopolysaccharide, outer membrane, cell membrane B) In Gram-negative bacteria: peptidoglycan, lipid membrane C) In acid fast bacteria: lipid layer, peptidoglycan, cell membrane D) In Gram-positive bacteria: peptidoglycan, lipid layer, cell membrane C The Gram Stain technique differentiates between cells with different amounts of ______ in their cell wall A) teichoic acid B) peptidoglycan C) lipotechoic acid D) glutamic acid B Endospores are usually induced to form when: A) temperatures are normal B) cells are growing in vegetative state C) essential nutrients are depleted D) water moves across cell membrane C Some bacteria can transfer DNA to another cell using: A) cilia B) conjugation pili C) axial filaments D) Lophotrichous flagella B A substance derived from one microorganism that kills or restricts the growth of other microorganisms is best described as a(n): A) poison B) antibody C) vaccine D) antibiotic D A Which of the following is the correct order of phases of growth in the growth curve of a batch culture? A) death/decline phase --> lag phase --> log phase --> stationary phase B) lag phase --> log phase --> stationary phase --> death/decline phase C) log phase --> lag phase --> stationary phase --> death/decline phase D) stationary phase --> log phase --> lag phase --> death/decline phase B A bacterial population grows most rapidly during ____ phase. A) stationary B) lag C) log D) death C In the stationary phase of bacterial growth: A) the number of newly generated cells is greater than the number of dying cells B) the number of newly generated cells is less than the number of dying cells C) the number of newly generated cells is the same as the number of dying cells D) none of the above C Neutral ph=7. Acidophiles would b expected to grow best at a pH of A) 3 B) 9 C) 7 D) 12 A Human pathogens are generally which type of microbe? A) mesophiles B)psychrophiles C) extreme thermophiles D) thermophiles A Which of the following is most likely to have evolved to live in the deep layers of mud, where there is a complete lack of free oxygen? A) Obligate aerobe B) obligate anaerobe C) facultative anaerobe D) aerotolerant anaerobe B Which type of cell will shift to aerobic metabolism when oxygen is available but will carry on fermentation when no oxygen is available? A) aerotolerant anaerobes B) facultative anaerobes C) obligate anaerobes D) obligate aerobes B Bacteria that ferment lactose grow as red colonies on MacConkey's agar while those that do not ferment lactose grow colorless and transparent. MacConkey's agar can best be describes as being: A) selective B) differential C) complex D) enriched B Sabourard's agar has a low pH which encourages the growth of molds and prevents the growth of bacteria. Sabourard's agar could best be described as being: A) selective B) differential C) complex D) enriched A The bacterial chromosome is located in which of the following? A) the capsule B) the nuclei region C) the nucleus D) the periplasmic space B During diffusion, molecules _____ A) move from hotter areas to cooler areas B) move from areas of higher concentration to areas of lower concentration C) move from areas of lower concentration to higher concentration D) expend energy to more around B A charged molecule which moves down its concentration gradient and across a protein channel in a cell membrane without energy being expended by the cell is experiencing ____. A) simple diffusion B) osmosis C) budding; bacteria D) budding; yeast A The autoclave uses which of the following mechanisms for sterilization? A) pressure B) temperature C) pressure and temperature D) pressure, temperature, and pH C Which of the following involves sterilization by heating steam in a jacket and subsequent entrance of the steam into a sterilization chamber, where materials and substances to be sterilized are placed in a/an: A) autoclave B) pasteurization chamber C) dry heat oven D) open flame A Which of the following actions would be most clearly considered bacteriostatic rather than bactericidal? A) autoclaving bacterial cultures B) placing a bacterial culture in the -80 degree C freezer C) spraying 70% alcohol on a laboratory bench D) gamma wave radiation B A candle jar would be used for growing: A) Gram-negative organisms B) halophiles C) thermophiles D) microaerophiles D Sterilization is the: A) killing or removal of all microorganism in a material or an object B) reduction of the number of pathogenic microorganisms in a material or an object C) killing or removal of some but not all microorganisms D) disinfection of living tissue A Disinfection is the _____ A) killing of viruses while only inhibiting fungi and bacteria B) killing or removal of all microorganism in a material or an object C) same as sterilization D) reduction of the number of pathogenic vegetative microorganisms D What is a chemical agent that can be used safely on living tissue to destroy microorganisms or to inhibit their growth? A) microwaves B) antiseptic C) disinfectant D) ionizing radiation B When food is salted, water diffuses ________ microorganisms, causing them to ____ and die. A) into; shrink B) into; explode C) out of; shrink D) out of; explode C What sterilization technique should be used for sterilizing plastic instruments? A) filtration B) disinfection C) ionizing radiation D) autoclaving C Which of the following is NOT a typical action of Chemical Microbial Control Agents? A) damage to proteins B) change exterior charge of cells C) damage to nucleic acids D) alteration of membrane permeability B Which of the following is true about Taxonomy of organisms we currently use? A) We still use the two categories defined by Linnaeus B) Organisms are defined in five kingdoms: Monera, Protista, Fungi, Plantae, Animalia C) Sorted into three domains, defined by relation of ribosomal RNA sequence C What is the cheapest, easiest, and most practical method to prevent the spread of disease? A) vigorous hand washing B) sterilizing all surfaces in a room C) was used by NASA in outer space D) breaks down the slime and matrix to allow antimicrobials better access to microbes D Use this information to answer the following question..... Which disinfectant was the least effective against Staphylococcus? A) phenol B) Cetylpyridinium chloride C) ethanol D) merthiolate C Plaque on teeth is an example of which of the following? A) a cavity B) extreme thermophiles C) a biofilm D) furuncles C How does Staphylococcus aureus cause gastrointestinal symptoms? A) by penetrating the stomach lining B) by reproducing in the intestines, causing enteritis C) by reproducing in the stomach, causing gastritis and ulcers D) by producing enterotoxins when growing in food D What is the scientific name of the unusual bacterium that can survive in the acidic environment of the stomach and is associated with peptic ulcers, as well as with increased risk of stomach cancer? A) Vibrio cholerae B) Escherichia coli O157:H7 C) Heliobacter pylori D) Salmonella typhi C What is a dangerous drop in blood pressure associated with infection called? A) bacteremia B) hypotensive shock C) sepsis D) septic shock D Which of the following best describes Borrelia burgdorferi? A) a bacillus that causes plague B) a coccus that causes cat scratch disease C) a spirillum that causes Rocky Mountain spotted fever D) a spirochete that causes Lyme disease D Which of the following describes impetigo? A) a systemic fungal infection caused by Candida spp.and otherspecies that is difficult to treat B) a highly contagious infection caused by Staphylococcus aureus and Streptococcus pyogenes that causes vesicles and pustules C) a mild and self-limiting viral infection that can be caused by a wide range of infectious agents D) a noncontagious rash (not caused by an infectious agent) that spreads rapidly across the skin B Which microbe causes streptococcal pharyngitis (strep throat)? A) S. aureus B) S. epidermidis C) S. pyogenes D) S. typhimurium C A microbial advantage that allows bacteria to cause strep throat symptoms includes A) coagulase enzyme B) waxy outer lipid layer C) release of exotoxins D) urease enzyme C A microbial advantage that allows digestive disease-causing bacteria to persist despite traditional cleaning methods in hospital acquired infections includes A) acidophilic bacteria B) spores formed by C. difficile C) Lipopolysaccharide toxin in E. coli D) salmonella penetration into intestinal epithelia B Which refers to pyuria? A) production of urine that contains blood B) production of urine that contains pus C) bladder pain D) painful urination B B Which of the following is true about glycolysis? A) There is a net loss of ATP after glycolysis B) the net yield is 2 ATPs for each molecule of glucose C) it provides cells with the largest amount of energy in metabolism steps D) ten molecules of ATP are used in the initial phosphorylation steps B The initial substrate molecule for the Krebs cycle is: A) glucose B) pyruvate C) acetyl-CoA D) carbon dioxide C After glycolysis in muscle cells, what is the final electron acceptor when there is a lack of oxygen? A) Lactic acid B) pyruvate C)ethanol D) NADH B The synthesis of proteins, in which amino acids are joined together to make a single large molecule, would be most correctly described as being a/n ________ reaction. A. cytobolic B. anabolic C. catabolic D. metabolic B Organisms which can fix Carbon into larger Carbon molecules are called: A. chemotrophs B. phototrophs C. heterotrophs D. autotrophs D Which is a common electron acceptor in catabolic reactions? A. ATP B. NAD+ C. NADH D. FADH2 B ATP synthase is located ___________ in prokaryotes, and it is found ____________ in eukaryotes. A.In outer cell membrane of gram negative cells only, on nuclear membrane B. In mitochondria, in mitochondria C. On cell membrane, in mitochondria D. On cell membrane, on nuclear membrane C Which of the following processes yields the most ATP? A. fermentation B. electron transport chain and chemiosmosis C. glycolysis D. Krebs cycle B What is the final fate of the Carbon after glycolysis, pyruvate processing, and Krebs Cycle? A. all Carbons have been oxidized to CO2 B. all Carbons have been reduced to CO2 C. half of the Carbons become acetylCoA, and the rest are oxidized to CO2 D. half of the Carbons become acetylCoA, and the rest are reduced to CO2 A A substrate analog is a chemical that looks very similar to the true substrate, such as PABA for the enzyme synthetase. How does the substrate analog affect synthetase? A. denatures the enzyme B. denatures, then rebaters the enzyme C. acts as a competitive inhibitor in the active site D. acts as an allosteric noncompletitive inhibitor changing the shape of active site C In the electron transport chain, the energy to make ATP comes from electrons and H+ protons from A. FADH2 B. NADH C. neither FADH2 nor NADH D. both FADH2 and NADH D In aerobic respiration, the final electron acceptor is: A. Carbon B. NADH C) removing an amino group from a nucleotide D) causing breaks in chromosomes B What are nucleosomes? A. subunits found in proteins B. subunits that combine to make DNA C. structures involved in chromosome condensation into chromatin D. enzyme machinery the cell uses to copy its DNA C Which of the following sequences tells a ribosome where to insert the first Methionine? A. Promoter B. AUG C. Origin D. UGA B Which of the following sequences tells DNA polymerase which strand to synthesize and in the correct direction? A. Promoter B. AUG C. Origin D. UGA C Reverse transcription occurs when: A. RNA is used as a template to produce DNA B. DNA is used as a template to produce RNA C. Protein is used as a template to produce RNA D. RNA is used as a template to produce protein A During replication DNA is synthesized by _____, and it synthesizes a new DNA molecule in a __________ direction. A. DNA polymerase, 5' --> 3' B. RNA polymerase, 5' --> 3' C. DNA polymerase, 3'--> 5' D. RNA polymerase, 3'--> 5' A An mRNA molecule contains three nucleotide (triplet) units called _____. These units are read by ribosomes. A. aminoacids B. bases C. codons D. anticodons C One strand of DNA runs from 5′ to 3′ and the opposing strand runs 3′ to 5′, meaning that the strands are oriented in which way? A. Antiparallel B. Anticomplementary C. Antihelical D. Semiconservative A` Polymerase chain reaction: A. involves cycling between 30C and 37C to unwind and copy DNA B. allows for the rapid amplification of a billion copies of DNA without needing a living cell C. uses RNA polymerase and ribosomes in a test tube D. uses DNA polymerase from human cells B Which ONE of the following statements is always TRUE? A. a mutation is always harmful B. changes in DNA always change the protein shape but not the function C. Changes in DNA lead to changes in protein function D. a change in DNA may change a protein's shape and function D Which of the following processes increases genetic variation seen in bacteria? A. Transformation B. Conjugation C. Transduction D. all of the above D The transfer of DNA between bacterial cells by a virus is: A. transformation B. transduction C. transferration D. conjugation B Which plasmid encodes the genes that cause bacterial conjugation? A. any plasmid B. Plasmids cannot be transferred by conjugation. During the process of lysogeny: A. a bacterium takes up DNA from the media B. a phage integrates into the chromosome of the bacterium, creating a prophage C. new phage particles are assembled in the host bacterium D. a bacterium is split open to release new phage particles B Which of the following processes requires contact between donor and recipient cells? A. transduction B. transcription C. conjugation D. transformation C DNA analysis in a genome study would not be an effective method to detect which type of pathogen? A. Bacteria B. fungi C. viruses D. prions D In an effective cloning strategy, transformed plasmids can be selected with media containing ____________, while recombinant plasmids with vector and insert can be screened using ________________. A. An antibiotic, a second antibiotic B. Blue-white color, anti fungal C. An antibiotic, blue-white color D. Blue-white color, an antibiotic C Using the Beta Galactosidase screening method, we would know that we have a possible successfully cloned recombinant DNA plasmid with insert if we see: A. a white colony. this has insert interrupting the lacZ gene B. a blue colony. this has no insert DNA interrupting the lacZ gene C. a blue colony. this has insert DNA interrupting the lacZ gene D. a white colony. this has no insert DNA interrupting the lacZ gene A Which of the following structures do viruses use to attach themselves and enter the host cells? A. viral spikes B.viral RNA C. viral RNA polymerase D. viral DNA A The main jobs all viruses must accomplish upon infecting a host cell include: A. Transform the cell and kill the cell B. Copy the viral DNA and cut the host DNA C. Copy the viral genome and express the viral genes D. Insert its RNA genome into the chromosome and reverse transcribe its proteins C A minus (antisense) strand RNA virus would most likely synthesize proteins within a host cell through the following synthesis pathway: A. antisense RNA --> sense RNA ---> protein B. antisense RNA--> protein C. antisense RNA--> DNA--> protein D. antisense RNA --> sense RNA --> DNA --> protein A Which of the following represents the correct order of steps in a typical virus replication cycle? A. maturation --> adsorption --> penetration --> release --> synthesis B. adsorption--> penetration--> release--> maturation--> synthesis C. adsorption-- > penetration--> maturation--> synthesis--> release D. adsorption--> penetration-- > synthesis--> maturation--> release D Enveloped animal viruses typically leave the host cell by: A. host cell lysis B. host cell rupture C. budding D. animal viruses never leave the host cell C Often, patients take multiple classes of antiviral drugs to fight HIV infection. Why is this necessary? A. using only medicine allows more genetic pressure to select for mutant HIV variants quickly, increasing risk of drug resistant HIV B. having multiple medicines helps block multiple steps, ensuring protection against viral replication C. reverse transcriptase is very error prone, quickly creating mutant versions that can evade one or more inhibitors D. all of the above D B. The vaccine causes a change in the virus, resulting in a new virus that is more infectious C. RNA genome becomes a DNA genome D. Surface proteins move to different locations on the virus surface A The reason influenza virus has antigenic drift is: a. the antibodies kill the surface proteins b. the proteins on the virus surface move around c. RNA genomes of two viruses that connect the same host cell can recombine d. the enzymes that copy the RNA genome make errors, causing mutations D A patient has symptoms of a common cold due to rhinovirus. They request an antibiotic. You tell them: A. Yes, antibiotics are the proper course of action to reduce viral infection B. Yes, anitbiotics will prevent the latent cold virus from becoming lytic C. No, antibiotics only kill arboviruses D. No, antibiotics are only appropriate if there is a secondary bacterial infection D Which of the following diseases does NOT involve a mosquito in its viral transmission? A. Rocky Mountain Spotted Fever B. Dengue Fever C. Zika D. Chikungunya A The best method for prevention of Eastern Equine Encephalitis is: A. Vaccine B. Antibiotics C.Antiviral therapy targeting reverse transcriptase D. Mosquito control D Predict the DNA sequence from the mRNA sequence provided. mRNA: 5' AUG ACU UAC UAG 3' A.5'AUG ACUUAC UAG3' B.5'ATG ACT TAC TAG3' C.3'TAC TGA ATG ATC5' D.5'TAC TGA ATG ATC3' C Predict the amino acid sequence from the mRNA sequence provided. Use genetic code on the last page. mRNA: 5' AUG ACU UAC UAG 3' A. Met Ile Tyr Stop B. Met Thr Ser Stop C. Met Ile Ser Stop D. Met Thr Tyr Stop D Imagine that DNA polymerase made a mistake copying the DNA sequence from the previous two questions. After RNA polymerase read the now mutated DNA, it caused the mRNA transcript to insert another G after the first codon (sequence now reads AUG GAC UUA CUAG). Which of the following statements is FALSE? A. The stop codon no longer works B. This is an example of a base pair substitution point mutation C. This is a frameshift mutation D. There are now two Leu(leucine) amino acids in the protein that were not there before. B Acquired Immune Deficiency Syndrome (AIDS) is caused by a retrovirus. Which of the following best represents the genetic information flow used by retroviruses? A. DNA--> mRNA-->protein B. DNA-->protein C. RNA-->DNA-->mRNA-->protein D. RNA--> protein C When Ebola virus replicates in a host cell, the cell becomes a virus production machine. Once the cell has produced many copies of the virus, holes in the cell membrane are created to release thousands of copies of the virus. This is an example of: A. Latency B. Lysis C. Vegetative growth D. Lysogeny B One of the long term health concerns with a DNA genome virus is: A.Recombination of viral genome into host cell genome B. RNA-dependent RNA polymerase and Reverse Transcriptase C. Antigenic Shift D. Antigenic Drift A Which of the following methods are currently being developed for a synthetic microbiology approach to helping patients with metabolic disorders? The process of removing lymphocytes which recognize self antigens, thus producing tolerance in the developing host immune system is: A.diapedisis B. memory C. clonal deletion D. opsonization C All of the following are components of the nonspecific host defenses EXCEPT: A. interferon B. immunoglubulin C. mucus D. complement B A multilobed lymphatic organ that functions to process lymphocytes known as T cells and release them into the blood is the: A. thymus gland B. tonsil C. thalamus D. Peyer's patches A Leukocytes responsible for killing virus infected cells in nonspecific immunity are _____. A.Eosinophils B. Monocytes C. natural killer cells D. T helper cells C All of the following have correctly matched antibody class with their function EXCEPT: A. IgA - found in saliva and breast milk B. IgD - acts as a T Cell receptor C. IgE - involved in allergy response D. IgM - early response to an antigen presented for first time B Which of the following cells has receptors on its surface and specifically recognizes virus- infected cells by viral antigens presented on MHC Class I? a. TD cells b. NK cells c. neutrophils d. TC cells D All of the following are types of vaccines except: a.purified active toxin b. killed whole bacteria c. toxoid d. live attenuated virus A Which of the following is NOT a traditional component of a vaccine? A. Adjuvant B. Stabilizers and Preservatives C. Recombinant Antigens D. Complement D Hypersensitivity or allergy refers to the immune system responding _____. A. With mast cells sensitized with IgE receptors B. Opsonization and compliment activation C. Bradykinin release and increased IgM production D. To its own tissues as if it was foreign A Immunodeficiency refers to the immune system responding _____. A. not strong enough to an antigen B. to its own tissues as if they were foreign C. in an exaggerated way to a foreign substance D. only with the MHCII receptor A The process whereby immune cells leave the blood by passing between the endothelial cells that line blood vessels is known as: A. Interferon activation B. phagocytosis C. sensitization D. diapedesis D Macrophages attacking bacteria at the site of infection is an example of: A. Viral Immunity B. Specific Immunity C. Non-specific immunity D. MacroImmunity C Complement can activate any of the following processes EXCEPT A. phagocytosis by macrophages B. Herd Immunity in a community is at 97% C. Vaccine is administered in a subcutaneous route D. The vaccine preparation includes an improved adjuvant A Blood type ______ is considered to be a universal recipient since ___________. A. AB, the individual has no A or B antigens on their red blood cells B. AB, the individual has no anti-A and anti-B antibodies C. O, the individual has no A or B antigens on their red blood cells D. O, the individual has anti-A and anti-B antibodies B Leukemia could be indicated after what kind of Whole Blood Cell Count results? A. Low Leukocytes B. Low Hematocrit C. High Platelets D. High Leukocytes D What makes the CRISPR-Cas9 system so precise? A. Cas9 enzyme only cuts RNA B. Cas9 enzyme cuts DNA better than other enzymes C. Cas9 enzyme recognizes the specific location to cut due to precise match of DNA and RNA sequences D. Cas9 enzyme recognizes the specific location to cut due to protein tag markers C A hospital patient just finished a strong course of antibiotics and then contracted C. dificile infection, causing bacterial diarrhea. What is a good remedy?A. A second course of antibiotics B. Fecal transplant from a healthy donor C. Antiprotozoan drugs D. Antiviral therapy B Killing virus-infected cells is an example of triggering the __________ immune response; this involves activation of ____________ immune cells. A. Humoral; plasma B. Humoral; cytotoxic T cells C. Cell-mediated; plasma cells D. Cell-mediated; cytotoxic T cells D Mast cells and basophils release which chemical signal involved in hypersensitivity type I? A. Interleukins B. Histamine C. Interferon D. Leucocidin B 33. Which molecular fragment on an antigen molecule do antibodies recognize and respond to? A. constant region B. complement C. variable region D. epitope D Individuals with type O blood have which of the following on the surface of their red blood cells? A. MHC Class II antigens B. the O glycoprotein antigen only C. modified A or B glycoprotein antigens that are unable to trigger an immune response D. neither A nor B glycoprotein antigens D Which technique is used to test whether patients who have received a flu vaccine are immune to a newly circulating flu virus? A. gel electrophoresis B. immunostaining C. hemagglutination D. western blotting C Which technique uses antibodies to identify the presence of a protein in a solution, such as presence of a food contaminant from a food preparation company? A. ELISA B. Hemagglutination C. Tissue Immunostaining D. RhoGam A A cell that has been infected with an intracellular pathogen will be targeted for destruction by which type of lymphocyte? A. B cell B. helper T cell C. cytotoxic T cell D. plasma cell RhoGam is administered to __________ mothers in their first pregnancy to prevent production of ________________ by the mother after delivery. A. Rh- ; Rh+ antigen B. Rh- ; Anti-Rh antibodies C. Rh+ ; Rh+ antigen D. Rh+ ; Anti-Rh antibodies B For the next two questions, select the order of events that happen in the specific immune system in response to a viral infection. Consider the following list of items: a) Macrophage phagocytoses the virus b) Skin cell phagocytoses the virus c) MHC class I presents the antigen d) MHC class II presents the antigen e) T helper cell receptor recognizes MHC class II with antigen f) T helper cell receptor recognizes MHC class I with antigen g) B cell is activated by MHC class I with antigen h) B cell is activated by T helper cell chemical messages i) B cell produces antibodies to target the original virus j) Cytotoxic T cell is activated by T helper cell chemical messages k) Cytotoxic T cell release toxic chemicals into infected skin cell When a virus is floating around in the interstitial fluid, but has not yet adsorbed to its target cell, which of the following best describes the sequence of events for the immune syste D When a virus has infected a skin cell and is hidden within that cell, which of the following best describes the sequence of events for the immune system: A. C,F,J,K B. B,D,E,J,K C. B,G,I D. A,D,E,J,K A Which of the following immune reactions is NOT known to attack a virus infected cell and/or loose virus in the interstitial fluid? A. Neutralization by antibodies B. IgE sensitization of Mast Cells C. NK cell attack D. Interferon production B The name of this test is ___________________, which is indicated by the completely filled circles that represent ___________________ A. ELISA; red blood cells that fell down to the bottom of the well B. ELISA; red blood cells crosslinked with flu virus C. Hemagglutination; red blood cells that fell down to the bottom of the well D. Hemagglutination; red blood cells crosslinked with flu virus D What do the results mean in Row B, column 1:1280? A. Not enough antibody is present. So, Viruses and Red Blood Cells crosslink into a mesh spread across entire well B. The lowest concentration of antibody that fully blocks interaction of virus and antibody. Blood cells fall to bottom of well. C. Virus 1 is not protected by last year's vaccine D. Virus 2 is protected by last year's vaccine even better than the original virus. A In the figure above, __________ represents the primary antibody, and it binds to the __________________. A. B; bacteria A B. C; bacteria A C. B; variable region of C D. C, constant region of B A Antibody ______ must be created in a different animal other than rabbits, and it recognizes _________ as its antigen. A. B;C B. B;A C. C;A D. C;B D What specific part of the "sandwich" above allows the antigen to be visible to the naked eye? A. A B. B C. C D. D D