Bitcoin Network and Its Transactions BDC Practice Questions (Page 1)

Questions 1–5

1. 1application · medium

   A developer is creating a Bitcoin transaction that spends a UTXO locked with a P2PKH script. What must the developer provide in the unlocking script (scriptSig) to satisfy the locking script?

   • AThe private key and the address.
   • BThe private key and the public key.
   • CThe address and the digital signature.
   • DThe public key and a digital signature created with the corresponding private key.
   Reveal Solution Discussion Select an answer first
2. 2application · medium

   A developer is building a Bitcoin wallet and needs to prevent double-spending. Which mechanism does the Bitcoin network use to prevent a user from spending the same UTXO twice?

   • ANodes check that each input references a UTXO that has not been spent in any other transaction in the blockchain or mempool.
   • BNodes require a unique digital signature for each transaction, and the signature is checked against a global registry.
   • CNodes require that each transaction be broadcast at least twice to ensure it is recorded.
   • DNodes require that each transaction include a timestamp that is later than any previous transaction from the same address.
   Reveal Solution Discussion Select an answer first
4. 3expert · hard

   A company wants to run a Bitcoin node that can validate transactions and blocks without trusting third parties, but they have limited bandwidth and disk space. Which approach best balances their constraints?

   • ARun an archival full node that stores the entire blockchain.
   • BUse a third-party API for validation instead of running a node.
   • CRun a pruned full node that stores only the UTXO set and recent blocks.
   • DRun a lightweight SPV node that only downloads block headers.
   Reveal Solution Discussion Select an answer first
5. 4application · medium

   A merchant accepts Bitcoin payments and wants to reduce the risk of double-spending. The merchant currently waits for 0 confirmations. What should the merchant do?

   • AWait for 1 confirmation, which guarantees finality.
   • BRequire the customer to provide a signed receipt.
   • CAccept the transaction immediately because the UTXO model prevents double-spending.
   • DWait for at least 6 confirmations before considering the payment final.
   Reveal Solution Discussion Select an answer first
6. 5application · medium

   A node receives a transaction that spends a UTXO. The node checks that the UTXO exists in its UTXO set, verifies the signature, and executes the locking script. All checks pass. What is the next step the node must take before relaying the transaction to its peers?

   • AAdd the transaction to the next block it mines.
   • BRelay the transaction to its peers.
   • CRemove the spent UTXO from its UTXO set immediately.
   • DWait for a block confirmation before relaying.
   Reveal Solution Discussion Select an answer first