Here’s a comprehensive Ethereum and Solidity multiple-choice quiz with 90 questions, covering topics from beginner to intermediate level. Each question has four options and one correct answer provided.
🧠 Ethereum and Solidity Quiz (90 MCQs with Answers)
📘 Section 1: Ethereum Basics (1–30)
- What is Ethereum primarily used for?
A. File sharing
B. Smart contracts and DApps ✅
C. Image hosting
D. Traditional banking. - What is Ether (ETH)?
A. A hardware component
B. A stablecoin
C. A token standard
D. The native cryptocurrency of Ethereum ✅ - Ethereum uses which consensus mechanism (before Ethereum 2.0)?
A. PoW ✅
B. PoS
C. DPoS
D. BFT - What does EVM stand for?
A. Ethereum Voting Machine
B. Ethereum Virtual Machine ✅
C. Elastic Virtual Machine
D. Elastic Voting Mechanism - Which language is most commonly used to write Ethereum smart contracts?
A. Python
B. Solidity ✅
C. Java
D. Ruby - What is “gas” in Ethereum?
A. Network bandwidth
B. A metric for contract complexity
C. Fuel for transactions and computation ✅
D. Ether balance - What are blocks in Ethereum?
A. Encrypted contracts
B. Bundles of transaction data ✅
C. Gas units
D. Tokens - What happens when gas runs out during a transaction?
A. Transaction is paused
B. Transaction fails and is reverted ✅
C. Transaction continues
D. Partial execution - Ethereum accounts are of two types:
A. Public and private
B. User and system
C. EOA and Contract ✅
D. Gas and No-Gas - Ethereum launched in:
A. 2012
B. 2013
C. 2014
D. 2015 ✅ - Which of the following is true about a payable function in Solidity?
A. It can receive Ether ✅
B. It can send Ether automatically
C. It is used for gas estimation
D. It returns an event by default - What is the smallest denomination of Ether called?
A. Wei ✅
B. Finney
C. Gwei
D. Mwei - What does require() do in Solidity?
A. It declares a function
B. It reverts the transaction if a condition fails ✅
C. It logs an event
D. It returns a fallback - Which Ethereum client is written in Go?
A. Parity
B. Geth ✅
C. Besu
D. OpenEthereum - Which keyword is used to define a public variable in Solidity?
A. let
B. var
C. public ✅
D. visible - What is a fallback function in Solidity?
A. A function that is always public
B. A function called when no other function matches ✅
C. A function that logs errors
D. A function to override modifiers - Which command is used to deploy contracts using Hardhat?
A. npx hardhat compile
B. npx hardhat test
C. npx hardhat run scripts/deploy.js ✅
D. npx hardhat init - What is a block in Ethereum?
A. A fixed-size data structure
B. A container of multiple transactions ✅
C. A cryptographic algorithm
D. A validation node - Which of the following is used for upgrading smart contracts?
A. ABI
B. Proxy pattern ✅
C. Gas estimation
D. Truffle - What is the purpose of ABI in Ethereum?
A. Compress contract bytecode
B. Define token supply
C. Interface between contract and frontend ✅
D. Generate gas reports - What is the gas limit?
A. The total Ether in a block
B. The amount of data in a transaction
C. The maximum gas allowed for execution ✅
D. Number of blocks mined per second - What is msg.sender in Solidity?
A. The contract owner
B. The miner’s address
C. The address that called the function ✅
D. The signer of a transaction - What does the keyword view signify in Solidity?
A. The function can only write to storage
B. The function can read but not write to state ✅
C. It returns no value
D. It sends Ether - What is the return type of a function that doesn’t return anything in Solidity?
A. uint
B. null
C. void
D. none ✅ - What does Truffle provide for Ethereum development?
A. Block scanning
B. IDE
C. Testing, compiling, and deploying framework ✅
D. Cloud wallet - What is the storage location of a mapping in Solidity?
A. Stack
B. Memory
C. Storage ✅
D. Calldata - What is the purpose of the constructor in Solidity?
A. Destroy contract
B. Initialize state on deployment ✅
C. Upgrade contract
D. Pause functions - Which of the following can emit events in Solidity?
A. Libraries
B. Contracts ✅
C. Constants
D. Fallback functions - How is inheritance supported in Solidity?
A. By linking libraries
B. Through interfaces
C. Using is keyword ✅
D. By using override only - What is the main difference between memory and storage in Solidity?
A. Memory is for constants
B. Memory is temporary, storage is persistent ✅
C. Storage is read-only
D. Memory is on-chain
📘 Section 2: Solidity Language (31–60)
- Solidity is a:
A. Compiled, high-level programming language ✅
B. Interpreted scripting language
C. Low-level language
D. Framework - What does pragma solidity ^0.8.0 mean?
A. Use only version 0.8.0
B. Use versions greater than 0.8.0
C. Use 0.8.0 or any higher compatible version ✅
D. Disable Solidity versioning - The keyword used to declare a contract is:
A. class
B. contract ✅
C. interface
D. pragma - To store Ether in a contract, which function modifier is used?
A. pure
B. view
C. payable ✅
D. constant - What is msg.sender?
A. Contract address
B. Caller of the function ✅
C. Miner address
D. Blockchain ID - What is the purpose of require() in Solidity?
A. Log output
B. Assert values
C. Revert if condition fails ✅
D. Import contracts
- What is the purpose of using interfaces in Solidity?
A. To add UI functionality
B. To inherit from abstract classes
C. To define a contract’s external functions without implementation ✅
D. To control Ether transfers - What type of value does a mapping return if the key is not found?
A. Reverts
B. Null
C. Zero-value of the value type ✅
D. Throws an error - What does keccak256() function do in Solidity?
A. Generates pseudorandom numbers
B. Encodes string to base64
C. Calculates the SHA-3 hash ✅
D. Performs digital signing - Which Solidity version introduced pragma ^0.8.0?
A. With overflow/underflow protections ✅
B. Added string slicing
C. Deprecated events
D. Introduced memory-only data - What is the default value of a boolean in Solidity?
A. 1
B. false ✅
C. null
D. 0x0 - Which type of variable is not stored on the blockchain?
A. public
B. memory ✅
C. storage
D. mapping - What does msg.value represent in a payable function?
A. The amount of tokens received
B. The sender’s balance
C. The amount of Wei sent with the call ✅
D. The block reward - How do you send Ether from a contract in Solidity >= 0.8.x?
A. address.transfer(amount)
B. address.send(amount)
C. payable(address).call{value: amount}(“”) ✅
D. address.deposit(amount) - What is an enum in Solidity?
A. A constant address
B. A data type that restricts variable to predefined values ✅
C. A fixed array
D. A form of hashing - Which statement is true about modifiers in Solidity?
A. Used only with fallback functions
B. Automatically handle errors
C. Reusable pre-function logic ✅
D. Provide event logs - What is the purpose of block.timestamp in Solidity?
A. The current time of the Ethereum network ✅
B. The timestamp of contract deployment
C. The hash of the block
D. Miner-provided nonce - How are constructor arguments passed during deployment?
A. Through a separate file
B. As metadata in bytecode ✅
C. They are ignored
D. Via fallback function - What does abi.encodePacked() return?
A. String
B. JSON
C. Bytes tightly packed ✅
D. Hash - What is the function of assert() in Solidity?
A. To test external conditions
B. To revert on failed internal error checks ✅
C. To send Ether
D. To prevent reentrancy - Which type of call is considered dangerous for reentrancy?
A. Static call
B. External function call ✅
C. Internal pure function
D. emit call - Which of the following Solidity types is dynamic?
A. uint256
B. address
C. bytes ✅
D. bool - What is the use of indexed keyword in Solidity events?
A. Allows filtering by that field ✅
B. Marks the field for deletion
C. Removes duplicates
D. Limits gas usage - What is OpenZeppelin used for?
A. Ethereum network setup
B. Testing token transfers
C. Standard, secure smart contract libraries ✅
D. Gas optimization - What does the fallback function not have?
A. A name ✅
B. Logic
C. An address
D. A return value - Which gas cost is higher in Ethereum?
A. Setting a variable to zero
B. Setting a new non-zero value ✅
C. Calling a pure function
D. Calling a view function - Which of the following causes a transaction to fail in Ethereum?
A. Reaching the block gas limit
B. Calling a non-existent address
C. Reverting inside the contract ✅
D. Having zero balance - What does a smart contract address depend on during deployment?
A. Deployer’s balance
B. Random nonce
C. Deployer’s address and nonce ✅
D. Chain ID - What is the default visibility of a function in Solidity?
A. public
B. internal ✅
C. private
D. external - What does memory keyword do in Solidity?
A. Saves data on-chain
B. Saves data in EVM logs
C. Temporarily stores data during function execution ✅
D. Encrypts a string
📘 Section 3: Intermediate Solidity & DApps (61–90)
- What is a fallback function in Solidity?
A. Main logic of contract
B. Default function called when no other matches ✅
C. Error handler
D. Token allocator - What is an event in Solidity?
A. A type of struct
B. A log on blockchain ✅
C. A function
D. A contract initializer - What does view modifier signify?
A. Can modify state
B. Can only call another contract
C. Reads blockchain state, cannot modify ✅
D. Sends ETH - Which standard is used for fungible tokens?
A. ERC-721
B. ERC-1155
C. ERC-20 ✅
D. ERC-1400 - What is keccak256 in Solidity?
A. A hash function ✅
B. Random number generator
C. Decryption algorithm
D. Compiler - Mapping in Solidity is used for?
A. Iteration
B. Database connection
C. Key-value storage ✅
D. Logging
📘 Section 3: Intermediate Solidity & DApps (continued)
- Which data type should you use for storing ETH or token balances?
A. int
B. string
C. uint256 ✅
D. bool - What happens if assert(false) is triggered?
A. Skips line
B. Contract continues
C. Reverts transaction and consumes all gas ✅
D. Logs error and exits gracefully - What is a constructor in Solidity?
A. A function that destroys a contract
B. A payable function
C. A function executed only once during contract deployment ✅
D. A fallback function - Which function transfers Ether safely in Solidity (0.8+)?
A. transfer()
B. send()
C. call{value: amount}(“”) ✅
D. sendEther() - Which of these keywords is used to define an interface in Solidity?
A. interface ✅
B. abstract
C. implement
D. define - What does the keyword memory mean in a function parameter?
A. Persistent storage
B. Temporary storage during execution ✅
C. Stack location
D. Blockchain storage - The function modifier onlyOwner is used for?
A. Checking token balance
B. Ensuring only the contract owner can call the function ✅
C. Verifying transactions
D. Pausing the contract - Which function is used to receive Ether in a contract?
A. receive() ✅
B. receiveEther()
C. getEther()
D. etherReceiver() - When should the fallback() function be defined?
A. To handle undefined function calls ✅
B. To transfer Ether
C. To initialize tokens
D. To manage errors - What is the visibility of a function that can be accessed internally and externally?
A. public ✅
B. private
C. internal
D. external - How do you return multiple values from a Solidity function?
A. Use arrays
B. Use structs
C. Use tuples ✅
D. It’s not possible - The keyword emit is used for?
A. Returning gas
B. Calling a fallback
C. Triggering events ✅
D. Declaring errors - What is OpenZeppelin?
A. Ethereum blockchain
B. Token
C. Security library for smart contracts ✅
D. Solidity compiler - Which type of contract can be inherited in Solidity?
A. Constant
B. Interface
C. Abstract ✅
D. Static - What is a reentrancy attack?
A. Mining manipulation
B. Calling another contract recursively before state update ✅
C. Gas refund
D. ETH overflow - What does the keyword payable allow?
A. Receiving Ether ✅
B. Storing data
C. Logging transactions
D. Protecting from overflow - What is SafeMath used for?
A. Gas optimization
B. Integer overflow protection ✅
C. Signature validation
D. Token management - What is Remix IDE used for?
A. DApp frontend
B. Wallet manager
C. Smart contract development and testing ✅
D. Database management - How to prevent overflows in Solidity 0.8+?
A. Use SafeMath
B. Manual checks
C. Built-in overflow checks ✅
D. OverflowFixer - What is a smart contract?
A. Web server
B. Decentralized application logic on blockchain ✅
C. Ethereum node
D. Token - Which data type is used for true/false logic?
A. string
B. uint
C. bool ✅
D. bytes - What’s the advantage of using libraries in Solidity?
A. External debugging
B. Avoid code duplication ✅
C. Reduce contract size
D. Add mining features - What does msg.value represent?
A. Sender’s address
B. ETH sent with transaction ✅
C. Gas used
D. Recipient balance - What is the role of a smart contract ABI?
A. Bytecode
B. Compilation
C. Interface for interacting with the contract ✅
D. Wallet generation
✅ End of Quiz
