Blockchain Smart Contract Fundamentals Questions and Answers

Question 1

A developer deploys a smart contract to the Ethereum mainnet.
After deployment, they discover a logical bug in one of the functions.
What is the primary consequence of blockchain's immutability in this scenario?

Accepted Answer

The contract's code is permanently unchangeable, and the bug cannot be directly fixed in the deployed version.

Answer

The contract can be paused by any user to prevent further use.

Answer

The developer can directly edit the contract's code on the blockchain to patch the bug.

Answer

The Ethereum network will automatically roll back the transaction that deployed the buggy contract.

Question 2

What is the primary function of the Ethereum Virtual Machine (EVM)?

Accepted Answer

To provide a sandboxed, deterministic execution environment for smart contracts.

Answer

To design the user interface for decentralized applications (dApps).

Answer

To encrypt transaction data before it is added to a block.

Answer

To facilitate cross-chain communication between Ethereum and other blockchains.

Question 3

A smart contract is designed to trigger an insurance payout for a flight delay. To function correctly, it needs to know the official landing time of a specific flight. How does a smart contract on a deterministic blockchain typically obtain this type of real-world information?

Accepted Answer

Through a trusted external data feed service known as a blockchain oracle.

Answer

By directly querying a public flight tracking API from within the contract code.

Answer

By allowing users to vote on the landing time after the fact.

Answer

By using a built-in time function within the EVM to access real-world clocks.

Question 4

A smart contract has a `withdraw` function where the code first sends Ether to the user's address and then updates the user's balance in the contract's storage. Which classic smart contract vulnerability does this specific order of operations create?

Accepted Answer

Reentrancy Attack

Answer

Integer Overflow

Answer

Timestamp Dependence

Answer

Denial of Service (DoS)

Question 5

Which of the following best describes the role of "gas" in the context of the Ethereum blockchain?

Accepted Answer

A unit of measurement for the computational effort required to execute operations.

Answer

A cryptographic token used exclusively for staking in Proof of Stake consensus.

Answer

A fixed-fee paid to the developers of a smart contract upon deployment.

Answer

The physical hardware required to run an Ethereum node.

Question 6

A developer is creating a decentralized autonomous organization (DAO) where token holders can vote on proposals. The smart contract automatically tallies votes and executes the winning proposal if a quorum is met. What fundamental property of smart contracts ensures this process will execute exactly as programmed without manual intervention?

Accepted Answer

Self-Execution

Answer

Anonymity

Answer

Scalability

Answer

Interoperability

A developer deploys a smart contract to the Ethereum mainnet.After deployment, they discover a logical bug in one of the functions.What is the primary consequence of blockchain's immutability in this scenario?

A developer deploys a smart contract to the Ethereum mainnet.
After deployment, they discover a logical bug in one of the functions.
What is the primary consequence of blockchain's immutability in this scenario?