Bitcoin and Bitcoin Blockchain Architecture BDC Practice Questions (Page 6)

Questions 26–30

1. 26foundation · easy

   What security property does Proof of Work provide to the Bitcoin network?

   • AIt ensures that all transactions are encrypted and private
   • BIt prevents any single entity from creating a new block
   • CIt makes it computationally expensive to rewrite history, protecting against double-spending
   • DIt guarantees that no transaction can ever be reversed
   Reveal Solution Discussion Select an answer first
2. 27application · medium

   A miner is trying to find a valid block. The miner has a block header with a fixed Merkle root and timestamp. The miner's hardware can try 1 terahash per second. What is the miner's primary task in each attempt?

   • AChange the Merkle root to find a hash below the target.
   • BChange the previous block hash to find a hash below the target.
   • CChange the timestamp until the hash is below the target.
   • DChange the nonce and hash the block header until the hash is below the current target.
   Reveal Solution Discussion Select an answer first
4. 28expert · hard

   A developer wants to create a Bitcoin smart contract that allows a payer to reclaim funds if the payee does not provide a secret within 100 blocks. Which Bitcoin Script construct should be used?

   • AA single signature from the payee, with no additional conditions.
   • BAn OP_RETURN output that stores the secret on-chain.
   • CA hashlock combined with a timelock (e.g., OP_CHECKLOCKTIMEVERIFY) in a script with two spending paths.
   • DA simple multisig script requiring both parties to sign.
   Reveal Solution Discussion Select an answer first
5. 29application · easy

   A developer is debugging a block parser and notices that the block header contains a field that commits to all transactions in the block. Which field is it?

   • AThe previous block hash
   • BThe nonce
   • CThe timestamp
   • DThe Merkle root
   Reveal Solution Discussion Select an answer first
6. 30foundation · easy

   Which property does a Merkle tree provide to the Bitcoin blockchain?

   • AFaster transaction confirmation by reducing block time
   • BConfidentiality of transaction amounts
   • CTamper-evidence: any change to a transaction changes the Merkle root
   • DAutomatic removal of invalid transactions from the block
   Reveal Solution Discussion Select an answer first