Blockchain Blockchain Other Certification CBDE Questions & Answers

• Question 41:

  Address.send():

  A. will cascade exceptions and address.transfer() will return a false on error.

  B. will return false on error while address.transfer() will cascade transactions.

  Correct Answer: B

• Question 42:

  A version pragma is a great way to make it clear:

  A. for which compiler version a smart contract was developed for. It helps to avoid breaking changes.

  B. for which blockchain a smart contract was developed for. It helps to avoid confusion with beta-customers.

  C. for which blockchain node a smart contract was developed for. It helps to avoid mixing up different versions of go-ethereum.

  Correct Answer: A

• Question 43:

  According to the official Style Guide:

  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 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.

  C. 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.

  Correct Answer: B

• Question 44:

  Events:

  A. are stored on chain and are a great way to get a return value when a contract calls another contract.

  B. are stored in something like a side-chain and cannot be accessed by contracts.

  C. are used primarily for debugging exceptions in solidity.

  Correct Answer: B

• Question 45:

  If a User calls contract A and that calls Contract B, then msg.sender in Contract B will contain the address of:

  A. the User.

  B. contract A.

  Correct Answer: B

• Question 46:

  Loops in Solidity:

  A. are a great way to circumvent gas requirements, because a loop will only consume gas once.

  B. are dangerous when used with data structures that grow, such as arrays or mapping, because it is hard to estimate the gas requirements.

  C. should be avoided where possible, because of unknown side-effects on the gas requirements.

  Correct Answer: B

• Question 47:

  You need to use ____________ to get the address that initiated the transaction.

  A. Tx.origin

  B. Msg.sender

  Correct Answer: A

• Question 48:

  The Fallback function:

  A. cannot receive Ether, not even by adding the payable modifier.

  B. can contain as much logic as you want, but it's better to keep it short and not exceed the gas stipend of 2300 gas.

  C. can be used to avoid receiving ether.

  Correct Answer: B

• Question 49:

  View and Pure Functions: A. can only be accessed during calls.

  B. can be accessed during transactions and calls.

  Correct Answer: B

• Question 50:

  View and Pure Functions:

  A. a function marked as pure can change the state, while a view function can only return static calls.

  B. a function marked as view can never access state variables, while pure functions are here to return only one value.

  C. a view function can access state variables, but not write to them. A Pure function cannot modify or read from state.

  Correct Answer: C