FREE Blockchain Smart Contract Development Questions and Answers

Question 1

Which of the following best describes the immutability of smart contracts once deployed on a blockchain?

Accepted Answer

Smart contracts cannot be modified or updated after deployment, making their code execution permanent.

Answer

Smart contracts can be updated by the original deployer using a specific administrative function.

Answer

Smart contracts can be modified through a decentralized autonomous organization (DAO) vote.

Answer

Smart contracts are only immutable for a fixed period, after which they can be upgraded.

Question 2

A developer is writing a Solidity smart contract that needs to store a collection of unique user IDs. Which data type or mapping would be most appropriate for efficiently checking if a user ID already exists?

Accepted Answer

`mapping(uint => bool)`

Answer

`uint[]`

Answer

`string[]`

Answer

`mapping(uint => uint)`

Question 3

What is the primary purpose of a 'fallback function' in a Solidity smart contract?

Accepted Answer

To execute code when a contract receives Ether without any data or a non-existent function is called.

Answer

To prevent any Ether from being sent to the contract address.

Answer

To provide a default return value for all functions if no explicit return is specified.

Answer

To allow the contract owner to pause all contract operations in an emergency.

Question 4

Consider a scenario where a Decentralized Autonomous Organization (DAO) smart contract is designed to manage community funds. The contract needs to allow members to propose spending initiatives and then vote on them. Which common smart contract design pattern would be most relevant for implementing the voting mechanism?

Accepted Answer

Voting Pattern

Answer

Upgradeability Pattern

Answer

Pausable Pattern

Answer

Access Control Pattern

Question 5

Which of the following tools is commonly used for compiling, deploying, and testing Solidity smart contracts in a local development environment?

Accepted Answer

Truffle Suite

Answer

Ganache

Answer

MetaMask

Answer

Remix IDE

Question 6

When developing a smart contract, what is the primary security risk associated with 'reentrancy attacks'?

Accepted Answer

An attacker repeatedly withdraws funds from a contract before its balance is updated.

Answer

An attacker gains unauthorized access to private variables within the contract.

Answer

An attacker can force the contract to execute arbitrary code.

Answer

An attacker can prevent legitimate users from interacting with the contract.