Blockchain Architecture and Its Core Components BBLC Practice Questions (Page 9)

Questions 41–45

1. 41application · medium

   A developer is building a blockchain and wants to ensure that the data in each block cannot be altered without changing the block's identity. What should she include in the block?

   • AThe public key of the block creator.
   • BA hash of the block's data, such as a Merkle root, stored in the block header.
   • CA timestamp of when the block was created.
   • DThe size of the block in kilobytes.
   Reveal Solution Discussion Select an answer first
2. 42application · medium

   A blockchain developer is designing a private blockchain for a supply chain consortium. Each member runs a full node. The developer wants to ensure that if an attacker modifies a transaction in an older block, the tampering is immediately detectable by any node that synchronizes from the network. Which architectural feature should the developer rely on as the primary defense?

   • AEach block header contains the hash of the previous block header, creating a cryptographic chain.
   • BAll nodes must run the same consensus algorithm to agree on the canonical chain.
   • CEach transaction is digitally signed by the sender's private key.
   • DThe ledger is replicated on every full node in the peer-to-peer network.
   Reveal Solution Discussion Select an answer first
4. 43foundation · easy

   Where are smart contracts stored on a blockchain?

   • AOn the nodes' local file systems only
   • BIn a separate off-chain database
   • CIn the blockchain itself, typically in a special transaction or account
   • DIn a central repository managed by the network administrator
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5. 44application · medium

   A company wants to automate the release of payment to a supplier when a shipment is delivered, without relying on a central authority. They plan to use a smart contract on a blockchain. What is required for the smart contract to execute automatically?

   • AThe smart contract is stored on a centralized server and executed by a trusted third party.
   • BThe smart contract code is stored on the blockchain, and nodes execute it when a triggering transaction is included in a block.
   • CThe smart contract is executed only when all parties manually approve each step.
   • DThe smart contract is compiled into a mobile app that runs on each party's phone.
   Reveal Solution Discussion Select an answer first
6. 45application · medium

   A node in a blockchain network receives a block that contains a transaction that the node has already seen in the mempool. What should the node do?

   • AIgnore the block and wait for a different block that contains new transactions only.
   • BBroadcast the transaction again to the network to confirm it is still pending.
   • CReject the block because the transaction is already known.
   • DValidate the block, and if valid, remove the transaction from its mempool and add the block to its chain.
   Reveal Solution Discussion Select an answer first