Bitcoin and Bitcoin Blockchain Architecture BDC Practice Questions (Page 8)

Questions 36–40

1. 36application · medium

   A developer is explaining to a stakeholder why a transaction that was included in a block might later be removed from the canonical chain. Which mechanism is responsible for this?

   • AA chain reorganization caused by a competing block with greater cumulative work
   • BThe transaction's locktime expiring
   • CThe UTXO being spent by a later transaction
   • DThe block reward being halved
   Reveal Solution Discussion Select an answer first
2. 37application · medium

   A startup wants to build a mobile Bitcoin wallet that can send and receive payments with minimal bandwidth and storage. The wallet does not need to validate the entire blockchain. Which node type should the wallet use, and what is its primary limitation?

   • AMining node; it validates transactions and creates new blocks.
   • BArchival node; it keeps the complete history of all transactions.
   • CLightweight (SPV) client; it relies on full nodes to provide transaction data and Merkle proofs.
   • DFull node; it stores the entire blockchain and validates all rules.
   Reveal Solution Discussion Select an answer first
4. 38foundation · easy

   Which of the following is an example of a simple smart contract enabled by Bitcoin Script?

   • AA smart contract that automatically executes a loan agreement with interest
   • BA token standard that allows creating new fungible tokens
   • CA decentralized autonomous organization that runs entirely on-chain
   • DA multi-signature wallet that requires 2-of-3 signatures to spend funds
   Reveal Solution Discussion Select an answer first
5. 39foundation · easy

   What happens to a UTXO when it is used as an input to a valid Bitcoin transaction?

   • AIt is permanently removed from the UTXO set and marked as spent
   • BIt is transferred to the miner as a transaction fee
   • CIt remains in the UTXO set but is flagged as 'in use'
   • DIt is duplicated and sent to both the recipient and the sender
   Reveal Solution Discussion Select an answer first
6. 40application · medium

   A developer is implementing a lightweight client that needs to verify that a specific transaction is included in a block without downloading the entire block. Which data from the block header and the transaction's proof should the client use?

   • AThe nonce and the timestamp from the block header
   • BThe block hash and the transaction's raw hex
   • CThe Merkle root and the Merkle proof (a set of sibling hashes)
   • DThe previous block hash and the difficulty target
   Reveal Solution Discussion Select an answer first