CCE Blockchain Fundamentals & Architecture 2

Question 1

What is the primary purpose of a Merkle tree in a blockchain block?

Accepted Answer

To efficiently verify transaction inclusion without downloading the full block

Answer

Merkle trees allow lightweight clients to verify a transaction exists in a block using only a logarithmic number of hashes (Merkle proof), without downloading all transactions.

Question 2

Which data structure does Ethereum use to store account state, enabling efficient updates and proofs?

Accepted Answer

Merkle Patricia Trie

Answer

Ethereum uses a Merkle Patricia Trie (a combination of Merkle tree and Patricia trie) to store world state, allowing efficient updates and cryptographic proofs of account balances.

Question 3

In the UTXO model used by Bitcoin, what does UTXO stand for?

Accepted Answer

Unspent Transaction Output

Answer

UTXO stands for Unspent Transaction Output — Bitcoin tracks balances as a set of unspent outputs rather than account balances, preventing double-spending.

Question 4

What happens to a blockchain when two miners simultaneously find valid blocks at the same height?

Accepted Answer

A temporary fork occurs and the chain with more cumulative work eventually wins

Answer

A temporary fork (orphan/uncle situation) occurs; nodes follow the heaviest chain rule so the branch accumulating more proof-of-work is eventually accepted as canonical.

Question 5

What is a 'genesis block' in a blockchain?

Accepted Answer

The first block in the blockchain, hardcoded with no predecessor

Answer

The genesis block is block #0, hardcoded into the protocol with no parent hash — it is the immutable foundation from which all subsequent blocks chain.

(CCE) Certified Cryptocurrency Expert Practice Test

(CCE) Certified Cryptocurrency Expert Practice Test

CCE Blockchain Fundamentals & Architecture 2