Download Certified Ethereum Developer (CED) Practice Exam Questions and more Exams Technology in PDF only on Docsity!
Question 1. What is the primary purpose of decentralization in blockchain technology? A) To increase transaction fees B) To distribute control and prevent single points of failure C) To centralize authority D) To slow down transaction speed Answer: B Explanation: Decentralization ensures that control is distributed among many participants, enhancing security and preventing single points of failure. Question 2. Which cryptographic hash function is used by Ethereum? A) SHA- 256 B) MD C) Keccak- 256 D) RIPEMD- 160 Answer: C Explanation: Ethereum uses Keccak-256 for hashing, which is different from Bitcoin’s SHA-256. Question 3. What is a key difference between Web2 and Web3 applications? A) Web3 apps are centralized B) Web2 apps use blockchain C) Web3 apps leverage decentralized networks and blockchain D) Web2 apps have no user interface Answer: C Explanation: Web3 applications utilize decentralized technologies like blockchains, unlike Web2’s centralized servers.
Question 4. What is immutability in blockchain? A) Data can be changed by any user B) Data cannot be altered once recorded C) Data is erased regularly D) Data is stored off-chain Answer: B Explanation: Immutability means that once data is added to the blockchain, it cannot be altered. Question 5. What is the main function of Merkle Trees in Ethereum? A) To store user accounts B) To organize transactions and validate data efficiently C) To handle consensus D) To set gas prices Answer: B Explanation: Merkle Trees allow efficient validation and organization of large data sets, such as transactions. Question 6. Which key generation algorithm does Ethereum use for account creation? A) RSA B) ECDSA (Elliptic Curve Digital Signature Algorithm) C) DSA D) SHA- 1 Answer: B Explanation: Ethereum relies on ECDSA for generating public and private keys.
A) To process credit card transactions B) To execute smart contract bytecode C) To mine blocks D) To generate wallets Answer: B Explanation: EVM is responsible for executing the code of smart contracts in the Ethereum ecosystem. Question 11. Which of the following best describes "Gas" in Ethereum? A) A token standard B) A fee for computation and storage C) A consensus mechanism D) A type of contract Answer: B Explanation: Gas is the fee required to perform computations and store data on the Ethereum network. Question 12. What does the opcode SSTORE do in the EVM? A) Reads data from storage B) Stores data in contract storage C) Calls another contract D) Sends Ether Answer: B Explanation: SSTORE is used to write data to a smart contract’s persistent storage. Question 13. What is the primary difference between CALL and DELEGATECALL opcodes? A) CALL sends Ether, DELEGATECALL cannot
B) CALL executes code in target’s context, DELEGATECALL in caller’s context C) Both do the same D) DELEGATECALL is deprecated Answer: B Explanation: DELEGATECALL executes code in the caller’s context, while CALL uses the target’s context. Question 14. What does the nonce in an Ethereum transaction prevent? A) Duplicate transactions B) Mining rewards C) Contract deployment D) Gas calculation Answer: A Explanation: Nonce ensures each transaction is unique and prevents replay attacks. Question 15. Which node type stores the entire blockchain history, including all states? A) Full Node B) Light Node C) Archive Node D) Validator Node Answer: C Explanation: Archive nodes maintain complete blockchain history and states. Question 16. Which of the following is an Ethereum testnet? A) Sepolia B) Mainnet
D) Account balance Answer: B Explanation: Higher gas prices incentivize miners/validators to include transactions sooner. Question 20. Which Ethereum network is used for live value transfers? A) Mainnet B) Ganache C) Goerli D) Rinkeby Answer: A Explanation: Mainnet is the official, live Ethereum network for real Ether and contracts. Question 21. In Solidity, what does the "pragma" keyword specify? A) Storage type B) Compiler version C) Contract name D) Function modifier Answer: B Explanation: Pragma sets the compiler version for the Solidity source code. Question 22. Which of the following is a value type in Solidity? A) Struct B) Mapping C) Integer D) Array
Answer: C Explanation: Integers are value types, which are stored directly in memory. Question 23. What does the "public" visibility keyword allow in Solidity? A) Only the contract can access B) Any external entity can access C) Only inheriting contracts can access D) No one can access Answer: B Explanation: Public functions and variables are accessible from outside the contract. Question 24. Which function modifier is used to restrict access to contract owner in Solidity? A) onlyOwner B) payable C) view D) pure Answer: A Explanation: onlyOwner restricts function execution to the contract’s owner. Question 25. What is the difference between "view" and "pure" functions in Solidity? A) View can modify state, pure cannot B) View reads state, pure cannot read or modify state C) Pure can modify state, view cannot D) Both can modify state Answer: B
Question 29. In Solidity, which keyword restricts function calls to the contract itself and inherited contracts? A) public B) external C) internal D) private Answer: C Explanation: Internal functions can be accessed only by the contract and its children. Question 30. Which data type in Solidity is used to store a group of related variables? A) Enum B) Struct C) Mapping D) Array Answer: B Explanation: Structs allow grouping of related variables under one type. Question 31. What does the "event" keyword denote in Solidity? A) A function call B) Logging mechanism for off-chain indexing C) State variable D) Data type Answer: B Explanation: Events are used to log contract activities for off-chain listeners.
Question 32. Which of the following is a reference type in Solidity? A) Integer B) Address C) Array D) Enum Answer: C Explanation: Arrays are reference types stored in memory or storage. Question 33. What is the purpose of the "fallback" function in Solidity? A) To mine blocks B) To handle Ether sent without data C) To store data D) To revert transactions Answer: B Explanation: Fallback functions receive Ether sent directly to the contract with no data. Question 34. Which keyword is used to declare a state variable in Solidity? A) function B) mapping C) uint D) contract Answer: C Explanation: State variables are declared with their type, such as uint, bool, etc.
A) extends B) inherits C) is D) implements Answer: C Explanation: The "is" keyword is used for inheritance in contract definitions. Question 39. What is the C3 Linearization rule used for in Solidity? A) Compilation B) Multiple inheritance resolution C) Gas calculation D) Event logging Answer: B Explanation: C3 Linearization ensures a consistent method resolution order in multiple inheritance. Question 40. What is an interface in Solidity? A) Contract with implemented functions B) Contract with only function declarations C) Contract with state variables D) Contract with events only Answer: B Explanation: Interfaces only declare functions without implementation for standardization. Question 41. What is the purpose of abstract contracts in Solidity? A) To deploy tokens
B) To define contracts with unimplemented functions C) To store Ether D) To emit events Answer: B Explanation: Abstract contracts include functions without implementations, serving as templates. Question 42. What does the "call()" function do when interacting with another contract? A) Executes code and forwards gas B) Sends Ether only C) Changes the compiler version D) Emits events Answer: A Explanation: "call()" executes code and can pass Ether and gas to another contract. Question 43. What is the primary risk of using "delegatecall" in contracts? A) Increased transaction speed B) Storage and context manipulation vulnerabilities C) Reduced gas cost D) No risk Answer: B Explanation: Delegatecall runs code in caller’s context, risking storage manipulation. Question 44. What is the main use of events in Solidity contracts? A) To store data B) To facilitate off-chain monitoring and indexing
D) Changing gas price Answer: A Explanation: TransferFrom lets one address transfer tokens on behalf of another given approval. Question 48. What vulnerability can occur if the same allowance is used repeatedly in ERC-20? A) Reentrancy B) Double-spend due to race condition C) Integer overflow D) Denial-of-service Answer: B Explanation: Race conditions in allowance can lead to double-spending attacks. Question 49. What is the ERC-721 token standard used for? A) Fungible tokens B) Non-fungible tokens (NFTs) C) Gas calculation D) Mining rewards Answer: B Explanation: ERC-721 standardizes NFTs, which are unique and indivisible. Question 50. Which function is unique to ERC-721 and not found in ERC-20? A) ownerOf B) totalSupply C) approve D) transfer
Answer: A Explanation: ownerOf returns the owner of a specific unique token in ERC-721. Question 51. What is the main benefit of ERC-1155 over ERC-20 and ERC-721? A) Lower gas cost for mining B) Supports both fungible and non-fungible tokens in one contract C) Only for NFTs D) No benefits Answer: B Explanation: ERC-1155 allows management of multiple token types within a single contract. Question 52. What is the purpose of Ethereum Improvement Proposals (EIPs)? A) To increase transaction fees B) To propose and standardize protocol upgrades C) To store data D) To mine blocks Answer: B Explanation: EIPs define and standardize new features or changes to the Ethereum protocol. Question 53. Which EIP introduced the ERC-20 standard? A) EIP- 721 B) EIP- 20 C) EIP- 1155 D) EIP- 2 Answer: B
Question 57. How can timestamp dependence introduce vulnerabilities in smart contracts? A) It slows down execution B) It allows manipulation of contract logic by adjusting timestamps C) It causes overflow D) It changes gas prices Answer: B Explanation: Relying on block.timestamp can allow miners/validators to manipulate contract outcomes. Question 58. What is a common cause of denial-of-service (DoS) in smart contracts? A) Unbounded loops causing excessive gas usage B) Using onlyOwner modifier C) Emitting events D) Setting low gas price Answer: A Explanation: Unbounded loops can exhaust gas, leading to DoS attacks. Question 59. What is the main risk with improper use of msg.sender in access control? A) Excess gas cost B) Unauthorized access to restricted functions C) Increased transaction speed D) Reduced contract size Answer: B Explanation: Not validating msg.sender properly can result in unauthorized access.
Question 60. How does the "pause" feature improve smart contract security? A) It increases gas cost B) It stops critical functions during emergencies C) It emits more events D) It allows contract upgrades Answer: B Explanation: Pausable contracts can disable sensitive functions during attacks or upgrades. Question 61. What is the proxy pattern used for in Ethereum contracts? A) To deploy tokens B) To enable contract upgradability C) To emit events D) To store data Answer: B Explanation: Proxy patterns allow contracts to be upgraded without changing their address. Question 62. What is the main difference between the Transparent and UUPS proxy patterns? A) Transparent proxies have separate admin logic, UUPS integrate upgrades in the implementation B) UUPS proxies cannot upgrade contracts C) Transparent proxies are deprecated D) UUPS proxies do not use delegatecall Answer: A Explanation: Transparent proxies separate admin functions, while UUPS integrates them in the contract. Question 63. What is a DAO in the context of Ethereum?
