Ethereum Virtual Machine BDC Practice Questions (Page 3)

Questions 11–15

1. 11expert · hard

   A smart contract has a function that calls an external contract. The external contract's function is expected to revert under certain conditions. The developer wants to catch the revert and continue execution, but also wants to avoid consuming all the gas in the sub-call. Which approach should be used?

   • AUse the transfer() function to send Ether to the external contract.
   • BUse a low-level call and check the returned boolean.
   • CUse the call() function with a high gas limit and rely on the EVM to refund unused gas.
   • DUse the send() function to call the external contract.
   Reveal Solution Discussion Select an answer first
2. 12expert · hard

   A team is designing a smart contract that must be deterministic across all nodes. They are considering using a random number generator that relies on the block timestamp. What is the main risk of this approach?

   • AThe block timestamp changes during the execution of a transaction.
   • BThe block timestamp can be manipulated by miners, making the random number predictable.
   • CThe block timestamp is not deterministic across nodes.
   • DThe block timestamp is not available in the EVM.
   Reveal Solution Discussion Select an answer first
4. 13expert · hard

   A developer is writing an inline assembly routine that needs to copy a 32-byte value from storage to memory. The developer wants to avoid using the stack for the intermediate value. Which opcodes should be used?

   • ASLOAD then MSTORE
   • BSLOAD then MLOAD
   • CMLOAD then SSTORE
   • DSSTORE then MLOAD
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5. 14expert · hard

   A developer is explaining to a colleague why the EVM is considered deterministic. Which statement best explains this property?

   • AThe EVM uses a random number generator that is seeded by the block hash.
   • BThe EVM always produces the same output for the same input and state.
   • CThe EVM runs on a single, centralized server.
   • DThe EVM's execution speed is the same on all machines.
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6. 15application · medium

   A developer is writing a low-level assembly routine to copy a 32-byte value from calldata to memory. Which sequence of EVM opcodes accomplishes this?

   • ACALLER, CALLDATALOAD, SSTORE
   • BCALLDATACOPY with appropriate offset and size arguments
   • CCALLDATASIZE, POP, MSTORE
   • DCALLDATALOAD, PUSH0, MSTORE
   Reveal Solution Discussion Select an answer first