Ethereum Virtual Machine BDC Practice Questions (Page 4)

Questions 16–20

1. 16foundation · easy

   What is the difference between a transaction that creates a contract and a transaction that calls a contract function?

   • AA creation transaction is mined by miners, while a call transaction is not
   • BA creation transaction has an empty 'to' field, while a call transaction specifies the contract address
   • CA creation transaction is signed by the contract, while a call transaction is signed by the user
   • DA creation transaction requires more gas than any call transaction
   Reveal Solution Discussion Select an answer first
2. 17expert · hard

   A developer is deploying a contract that uses a proxy pattern. The proxy delegates calls to an implementation contract. During an upgrade, the implementation contract is replaced. What happens to the storage variables of the proxy contract?

   • AThey are deleted to avoid conflicts.
   • BThey are reset to their initial values.
   • CThey are migrated to the new implementation contract.
   • DThey remain unchanged because storage is stored in the proxy contract.
   Reveal Solution Discussion Select an answer first
4. 18application · medium

   A smart contract function needs to return a dynamically-sized array of uint256 values to the caller. The array is built during the function execution. Where should the array be stored to minimize gas costs while still being accessible to the caller?

   • AOn the stack, since it is a small array.
   • BIn memory, and then return it via the ABI encoding.
   • CIn a temporary contract's storage.
   • DIn storage, so it persists after the call.
   Reveal Solution Discussion Select an answer first
5. 19foundation · easy

   What is a key difference between EVM storage and EVM memory?

   • AStorage is persistent and expensive, while memory is volatile and cheaper
   • BMemory is persistent across transactions, while storage is not
   • CStorage is limited to 1024 bytes, while memory is unlimited
   • DStorage is faster to access than memory
   Reveal Solution Discussion Select an answer first
6. 20foundation · easy

   What happens to the state changes made by a smart contract when it encounters a REVERT opcode?

   • AAll state changes are rolled back to the state before the transaction began
   • BThe contract is permanently deleted
   • CThe state changes are kept but the transaction is marked as failed
   • DOnly the changes made after the last SLOAD are rolled back
   Reveal Solution Discussion Select an answer first