A developer is writing a contract that needs to store a large amount of data. They are considering using a mapping of bytes32 to bytes32. What is the gas cost implication of storing a new key-value pair?

It costs 0 gas because mappings are free.

It costs 2,100 gas for the initial storage write.

It costs 5,000 gas for the initial storage write.

It costs 20,000 gas for the initial storage write.

A smart contract function is designed to transfer tokens only if the recipient is not blacklisted. The developer wants to ensure that if the recipient is blacklisted, the entire transaction is rolled back and no state changes persist. Which EVM mechanism should be used?

Throw a custom error using the THROW opcode.

Return a boolean false from the function.

A developer is deploying a contract that includes a loop iterating over an unbounded array. The team is concerned about the transaction running out of gas. What is the best practice to mitigate this risk?

Use a fixed-size array to guarantee the loop terminates within the gas limit.

Use a recursive function instead of a loop to distribute gas costs.

Increase the gas limit for the transaction to ensure the loop completes.

Avoid unbounded loops by using a paginated or pull-based design.

What is the primary purpose of gas in the Ethereum network?

To encrypt transaction data for privacy

To meter the computational work performed by transactions and smart contract execution

To serve as the native cryptocurrency for paying transaction fees

To store the state of all smart contracts

EC-CouncilBlockchain Developer Certification

Domain 5Objective 2

Ethereum Virtual Machine BDC Practice Questions (Page 2)

Part of the Ethereum and Smart Contract Development domain, which makes up ~11% of our current practice bank.

43questions here

9free pages

7concepts

Questions 6–10

6expert · hard
A developer is writing a contract that needs to store a large amount of data. They are considering using a mapping of bytes32 to bytes32. What is the gas cost implication of storing a new key-value pair?
Select an answer first
7application · medium
A smart contract function is designed to transfer tokens only if the recipient is not blacklisted. The developer wants to ensure that if the recipient is blacklisted, the entire transaction is rolled back and no state changes persist. Which EVM mechanism should be used?
Select an answer first
8application · medium
A developer is deploying a contract that includes a loop iterating over an unbounded array. The team is concerned about the transaction running out of gas. What is the best practice to mitigate this risk?
Select an answer first
9foundation · easy
What is the primary purpose of gas in the Ethereum network?
Select an answer first
10application · medium
A developer is writing a function that transfers Ether to a contract. The developer wants to ensure that if the recipient contract's fallback function reverts, the entire transaction is rolled back. Which Solidity construct should be used?
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