Ethereum Virtual Machine BDC Practice Questions (Page 9)

Questions 41–43

1. 41application · medium

   A developer is writing a function that calls an external contract. They want to handle the case where the external call fails without reverting the entire transaction. Which Solidity construct should they use?

   • Aassert() to verify the call succeeded
   • BUse low-level call and ignore the return value
   • Ctry/catch around the external call
   • Drequire() to check the return value
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2. 42expert · hard

   A developer is designing a contract that must be as gas-efficient as possible. They are choosing between using a mapping and an array to store a list of unique addresses. The list is expected to grow to thousands of entries. Which choice is more gas-efficient for checking if an address is already in the list?

   • AMapping, because lookups are O(1) and do not require iteration.
   • BBoth are equally efficient because they use the same storage.
   • CArray, because it uses less storage for large lists.
   • DArray, because iterating is cheaper than mapping lookups.
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3. 43foundation · easy

   Which EVM data area is volatile and cleared after each transaction execution?

   • AMemory
   • BStack
   • CCalldata
   • DStorage
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