Blockchain and Crypto Blockchain Fundamentals & Architecture 3

Question 1

What is the role of a full node in a blockchain network?

Accepted Answer

To store and independently validate the complete blockchain history and enforce all consensus rules

Answer

To store only block headers and rely on peers for transaction data

Answer

To specialize exclusively in mining new blocks and broadcasting them

Answer

To serve as a relay node routing transactions between mining pools

Question 2

What is 'gas' in the Ethereum network?

Accepted Answer

A unit representing the computational effort required to execute a transaction or smart contract, paid in ETH

Answer

The electricity cost metric used to measure miner profitability

Answer

The block reward granted to Ethereum validators for each block produced

Answer

The unit used to measure the data size of an Ethereum transaction

Question 3

What does UTXO stand for, and how is it used in Bitcoin?

Accepted Answer

Unspent Transaction Output — the unconsumed output of a past transaction used as input for new ones

Answer

Universal Token eXchange Output — a standard for cross-chain transfers

Answer

Unified Transaction eXchange Operation — a protocol for atomic swaps

Answer

User Transaction eXchange Override — a mechanism to reverse unconfirmed transactions

Question 4

What is a '51% attack' on a blockchain network?

Accepted Answer

When a single entity controls more than half the network's consensus power and can manipulate recent transaction history

Answer

A DDoS attack that takes 51% of network nodes offline simultaneously

Answer

A social engineering attack targeting 51% of blockchain wallet holders

Answer

A scenario where 51% of proposed transactions fail validation in a single block

Question 5

Which of the following best describes a distributed ledger?

Accepted Answer

A database replicated and synchronized across multiple locations with no single central administrator

Answer

A shared spreadsheet accessible to employees across different bank branches

Answer

A centralized database that allows read access from distributed locations

Answer

A private ledger distributed exclusively among licensed financial institutions

Question 6

What role does the SHA-256 algorithm play in Bitcoin?

Accepted Answer

It produces fixed-length hash outputs used in Proof of Work mining and transaction integrity verification

Answer

It encrypts private keys stored in Bitcoin wallets

Answer

It compresses raw transaction data to reduce storage requirements

Answer

It generates pseudorandom wallet addresses from user-supplied seeds

Question 7

What is the 'mempool' in a blockchain network?

Accepted Answer

A queue of broadcast but unconfirmed transactions waiting to be selected and included in a block

Answer

A pool of memory allocated on each node for caching recent block data

Answer

A collection of registered mining pools competing for the next block reward

Answer

A reserve of cryptocurrency held in escrow by the network's validator set