CBSA Smart Contracts & Decentralized Applications 2

Question 1

Which Solidity visibility modifier makes a function callable only from within the contract itself and not from derived contracts?

Accepted Answer

private

Answer

The `private` modifier restricts function access to the defining contract only, excluding derived contracts.

Question 2

In Ethereum smart contracts, what is a 'reentrancy attack'?

Accepted Answer

An external contract recursively calling back into the victim contract before state updates complete

Answer

Reentrancy attacks occur when a malicious contract calls back into the victim before its state (like balance) is updated, draining funds.

Question 3

What does the ERC-721 standard define?

Accepted Answer

A standard for non-fungible tokens (NFTs) on Ethereum

Answer

ERC-721 defines the standard interface for non-fungible tokens, where each token has a unique identifier.

Question 4

Which design pattern separates a smart contract's logic from its data storage to enable upgradability?

Accepted Answer

Proxy pattern

Answer

The proxy pattern delegates calls to a logic contract while keeping state in the proxy, allowing the logic to be replaced without changing the storage address.

Question 5

What is the purpose of the `require` statement in a Solidity smart contract?

Accepted Answer

To validate conditions and revert the transaction if the condition is false

Answer

`require` validates inputs or conditions and reverts the transaction with an optional error message if the condition fails.

(CBSA) Certified Blockchain Solution Architect Practice Test

(CBSA) Certified Blockchain Solution Architect Practice Test

CBSA Smart Contracts & Decentralized Applications 2