Ethereum Virtual Machine BDC Practice Questions (Page 5)

Questions 21–25

1. 21expert · hard

   A developer is writing a contract that uses require() to validate inputs. They want to provide a custom error message to the user. What is the most gas-efficient way to do this?

   • AUse assert(false) with a comment.
   • BUse revert() with a string literal.
   • CUse a custom error with parameters.
   • DUse require(false, "Error message")
   Reveal Solution Discussion Select an answer first
2. 22application · medium

   A user sends a transaction to a smart contract function that performs a state change and then calls an external contract that reverts. The user set a gas limit of 100,000 and the transaction consumed 80,000 gas before the revert. What happens to the remaining 20,000 gas?

   • AIt is returned to the user.
   • BIt is added to the block reward.
   • CIt is burned and not returned to the user.
   • DIt is transferred to the external contract.
   Reveal Solution Discussion Select an answer first
4. 23foundation · easy

   Which characteristic best describes the EVM's stack-based architecture?

   • AIt uses a last-in, first-out (LIFO) stack for most operations
   • BIt stores all data in a large associative array
   • CIt relies on a register-based architecture for speed
   • DIt uses a first-in, first-out (FIFO) queue for all data
   Reveal Solution Discussion Select an answer first
5. 24foundation · easy

   Why is the EVM considered deterministic?

   • ABecause it always executes transactions in the same order
   • BBecause it uses a random number generator for each execution
   • CBecause it runs on a single, centralized server
   • DBecause the same transaction with the same input will always produce the same output on any node
   Reveal Solution Discussion Select an answer first
6. 25application · medium

   A smart contract function needs to temporarily store a large data structure during execution and then discard it. The developer wants to minimize gas costs. Where should this data be stored?

   • AIn memory, because it is volatile and cheaper than storage.
   • BOn the stack, because it has unlimited capacity.
   • CIn storage, because it is persistent and cheap to write.
   • DIn calldata, because it is read-only and free.
   Reveal Solution Discussion Select an answer first