CBSA Smart Contracts & Decentralized Applications 4

Question 1

What is the role of an oracle in a decentralized application ecosystem?

Accepted Answer

To provide external real-world data to smart contracts that cannot access off-chain information natively

Answer

Oracles bridge the gap between blockchains and the external world, feeding data like prices or weather into smart contracts.

Question 2

Which ERC standard extends ERC-20 to allow token approvals and transfers to be performed in a single transaction via off-chain signatures?

Accepted Answer

ERC-2612

Answer

ERC-2612 adds a `permit` function that uses EIP-712 typed signatures to set allowances without a separate on-chain approval transaction.

Question 3

In the context of Ethereum smart contracts, what does 'immutability' imply about deployed bytecode?

Accepted Answer

The contract's code cannot be modified after deployment, only its state can change

Answer

Once deployed, a contract's bytecode is permanently stored on-chain and cannot be altered; only its state variables can change through function execution.

Question 4

What is a 'flash loan' in DeFi and what unique property enables it?

Accepted Answer

An uncollateralized loan that must be borrowed and repaid within the same transaction, enforced by smart contract atomicity

Answer

Flash loans exploit atomic transaction execution — if the loan is not repaid by the end of the same transaction, the entire transaction reverts.

Question 5

Which Solidity keyword marks a function as not modifying contract state, allowing it to be called without a transaction?

Accepted Answer

view

Answer

Functions marked `view` promise not to modify state and can be called off-chain for free using `eth_call`.

(CBSA) Certified Blockchain Solution Architect Practice Test

(CBSA) Certified Blockchain Solution Architect Practice Test

CBSA Smart Contracts & Decentralized Applications 4