CBDE 無料問題集「Blockchain BTA Certified Blockchain Developer - Ethereum」

（A）are interrupting execution on error, because they throw an exception.

（B）returning Booleans to indicate an error during execution.

（C）.send() throws an exception, while the other functions are returning Booleans during execution to indicate an error.

（D）continuing execution on error silently, which is the reason why they are so dangerous.

（A）to check input arguments from users.

（B）to check internal states that should never happen.

（A）all public and private state variables, public, internal and external functions, but not modifiers

（B）all public state variables and properties, public functions and modifiers, but not internal, external or private ones.

（C）all public state variables and properties, public and internal functions and modifiers.

（A）bytes32(string1) == bytes32(string2)

（B）string1 == string2

（C）the internal function "str_compare(str1,str2)"

（D）you can't directly compare two strings, but one method would be to hash both strings and compare the hashes.

（A）a string

（B）a 20 characters long hex number

（C）a 32 bytes value

（D）a 20 bytes value

（A）you should capitalize function names, events and contract names, to avoid confusion with JavaScript. You should use Tabs to indentation and a maximum of 80 characters per line.

（B）contract should be mixedCase, as well as function names. Events should be capitalized. 2 spaces should be used as indentation and a maximum of 120 characters per line.

（C）contract names should be capitalized, while functions should be mixedCase. You should use 4 spaces as indentation and a maximum of 79 (or 99) characters per line.

（A）750,000,000,000 Wei

（B）750,000,000 Wei

（C）750,000,000,000,000 Wei

（D）A flat fee of 1 Ether

（A）useful when developing distributed applications with HTML and JavaScript, because it already implements the abstraction of the JSON-RPC interface of Ethereum Nodes.

（B）necessary when developing distributed applications with HTML and JavaScript, because the proprietary JSON-RPC interface of Ethereum Nodes is a closed source.

（A）you need an external helper variable.

（B）can use the length parameter of the mapping.

（C）you cannot iterate any mapping to make the overall language design more safe.

（A）its best to use a contract with public storage variables, so it can be used like a class.

（B）it's not possible to generate new datatypes in Solidity.

（C）it's best to use a struct, which is cheaper than deploying a new contract.