Contract Lifecycle: Design, Development, and Deployment BDC Practice Questions (Page 4)

Questions 16–20

1. 16application · medium

   A developer is designing a smart contract that will hold user funds. The contract must minimize the risk of reentrancy attacks. Which design choice is most effective?

   • AMake the withdraw function private
   • BUse the checks-effects-interactions pattern and update balances before making external calls
   • CUse a low-level call without checking the return value
   • DUse a modifier that only allows the owner to call the withdraw function
   Reveal Solution Discussion Select an answer first
2. 17foundation · easy

   In Solidity, which data type is used to store an Ethereum address?

   • Astring
   • Baddress
   • Cbytes32
   • Duint160
   Reveal Solution Discussion Select an answer first
4. 18application · medium

   After deploying a Solidity contract to the Ethereum mainnet, a developer wants to verify the source code on Etherscan so users can read the contract and interact with it. Which step is required for verification?

   • AProvide the transaction hash of the deployment.
   • BProvide the private key of the deployer account.
   • CProvide the ABI and the contract address only.
   • DProvide the flattened source code and the exact compiler version used to deploy.
   Reveal Solution Discussion Select an answer first
5. 19foundation · easy

   Which design principle is most important for a smart contract that will hold funds and be deployed permanently on the Ethereum mainnet?

   • APrioritizing security over convenience, because deployed contracts are immutable and vulnerabilities can be exploited.
   • BDesigning for upgradeability from the start, because all smart contracts should be upgradeable to fix bugs.
   • CUsing the latest Solidity features, because newer versions are always more secure than older ones.
   • DMaximizing gas efficiency at the expense of readability, because lower gas costs are always the primary goal.
   Reveal Solution Discussion Select an answer first
6. 20application · medium

   A developer deployed a contract to the Ethereum mainnet and wants to verify its source code on Etherscan so users can read the contract and interact with it through the block explorer. What must the developer provide to Etherscan?

   • AThe flattened Solidity source code, compiler version, and optimization settings used during deployment
   • BThe contract's address and the deployer's public key
   • CThe contract's ABI and the deployer's private key
   • DThe contract's bytecode and the transaction hash of the deployment
   Reveal Solution Discussion Select an answer first