Blockchain CBDE 問題集

質問 1：
Gas costs accrue on sending a transaction:
A. only with a new smart contract deployment.
B. only interacting with an already deployed smart contract.
C. no matter the content.
正解：C

質問 2：
Unit-Testing on a local chain is important, because it helps you:
A. to run tests quickly and especially for free, compared to continuous deployment on the MainNetwork. This way you save a lot of fees, time and costs.
B. to run tests in an environment where logging is activated. On the Main-Net you have no access to transaction logs and this is ultimately the information you need to debug your contracts.
C. to avoid regression bugs with contracts that are updated constantly on the main-net. Once you update a contract on the main-net, the address stays the same, but the code changes and this can have disastrous side-effects.
正解：A

質問 3：
Function and Variable Visibility:
A. a function that is marked as internal cannot be called by other contracts, unless the function is used by a derived contract. Private Functions cannot be called by any other outside contract and public variables are generating automatically a getter function.
B. a function that is marked as external can never be called internally. Private functions can also be called by derived contracts using inheritance. Private variables are accessible also in derived contracts.
正解：A

質問 4：
Solidity gets compiled:
A. to bytecodes which are essentially opcodes running instruction by instruction.
B. to bytecode that can't be understood by humans.
正解：A

質問 5：
To send ether to a contract without a function call:
A. a fallback function must be declared and it must be made payable. If there is no fallback function or the fallback function is not payable it will throw an exception.
B. either a fallback function which is payable exists, or no fallback function at all exists.
C. you cannot send ether to a contract without explicitly calling a function. The fallback function can never receive ether.
正解：A