C4 Mining & Consensus Mechanisms 3

Question 1

In Proof of Authority (PoA), who is authorized to validate transactions and produce blocks?

Accepted Answer

A set of pre-approved validators with verified real-world identities

Answer

Any node that stakes a minimum threshold of the native token

Answer

Randomly selected nodes weighted by their historical transaction accuracy

Answer

Miners who solve a reduced-complexity Proof of Work puzzle

Question 2

What does 'finality' mean in the context of blockchain consensus?

Accepted Answer

The guarantee that a confirmed transaction cannot be reversed or reorganized out of the chain

Answer

The process of permanently archiving and deleting old transaction records

Answer

The maximum number of transactions a single block can contain

Answer

The point at which all mining rewards for a given block have been fully distributed

Question 3

What is the primary environmental criticism directed at Proof of Work mining?

Accepted Answer

PoW mining consumes massive amounts of electricity, contributing significantly to carbon emissions

Answer

Mining hardware produces toxic chemical waste that pollutes local environments

Answer

Mining operations monopolize rare earth metals needed for other essential industries

Answer

Mining hardware generates radio frequency interference that disrupts local communications

Question 4

What is the 'mempool' in a blockchain network?

Accepted Answer

A waiting area holding unconfirmed transactions broadcast to the network before block inclusion

Answer

A storage pool where accumulated mining rewards are held before distribution to miners

Answer

The portion of a node's memory allocated specifically to executing smart contract code

Answer

A shared encrypted database where node operators securely store their private keys

Question 5

What is 'Nakamoto Consensus' as established in the Bitcoin protocol?

Accepted Answer

Bitcoin's rule that the chain with the greatest cumulative proof of work is always the valid canonical chain

Answer

A governance model stating that Satoshi Nakamoto's original rules can never be changed by the community

Answer

A hybrid PoW/PoS system described in the original Bitcoin whitepaper for future scalability

Answer

A multi-signature protocol requiring consensus from a quorum of designated key holders

Question 6

What is an 'orphan block' (also called a stale block) in the context of mining?

Accepted Answer

A valid block that was excluded from the main chain because a competing block was accepted first

Answer

A block containing no transactions that was mined purely to collect the block reward

Answer

A block that failed network validation due to containing an invalid transaction signature

Answer

The genesis block of a newly forked blockchain that has no recognized parent block

Question 7

Which statement best describes the 'longest chain rule' in Proof of Work blockchains?

Accepted Answer

Nodes always follow the chain with the greatest accumulated cumulative proof of work

Answer

Nodes reject any block that contains more transactions than the immediately preceding block

Answer

The blockchain with the highest total transaction volume processed is considered the authoritative chain

Answer

Validators must confirm each block's height is strictly greater than all previously seen blocks