Blockchain Developer Token Standards and NFTs 3

Question 1

Which ERC-20 function approves a spender to transfer tokens on the owner's behalf?

Accepted Answer

approve

Answer

transfer

Answer

mint

Answer

burn

Question 2

What known issue affects the classic ERC-20 approve function when changing a non-zero allowance?

Accepted Answer

The approve race condition (front-running) double-spend risk

Answer

Reentrancy in mint

Answer

Integer overflow in totalSupply

Answer

Loss of decimals

Question 3

Which standard adds gasless approvals to ERC-20 tokens via off-chain signatures (permit)?

Accepted Answer

ERC-2612

Answer

ERC-721

Answer

ERC-1155

Answer

ERC-165

Question 4

What does the ERC-20 decimals function represent?

Accepted Answer

The number of decimal places used to display token amounts

Answer

The total token supply

Answer

The contract version

Answer

The number of holders

Question 5

Why can sending ERC-20 tokens directly to a contract not expecting them cause loss?

Accepted Answer

Plain transfer has no callback, so the contract may not register the deposit

Answer

The contract auto-refunds

Answer

Gas is refunded to the sender

Answer

Tokens are burned automatically

Question 6

Which standard, ERC-777, adds hooks that notify contracts on token sends and receives?

Accepted Answer

ERC-777

Answer

ERC-721

Answer

ERC-4626

Answer

ERC-20

Question 7

What security concern do ERC-777 receive hooks introduce that plain ERC-20 does not?

Accepted Answer

Reentrancy via the callback during transfer

Answer

Higher decimals

Answer

Loss of totalSupply

Answer

Inability to approve