Blockchain CBDE Exam Practice Test Instant Access

Question 1

All low-level functions on the address, so address.send(), address.call.valueQQ, address.callcode and address.delegatecall:

Aare interrupting execution on error, because they throw an exception.

Bcontinuing execution on error silently, which is the reason why they are so dangerous.

Creturning Booleans to indicate an error during execution.

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

Answer : C

Question 2

Checking the balance of an address inside a loop of a smart contract constantly:

Adoesn't cost any gas.

Bcost gas every time we check the balance.

Answer : B

Question 3

Using selfdestruct(beneficiary) with the beneficiary being a contract without a payable fallback function:

Awill throw an exception, because the fallback function is non-payable and thus cannot receive ether.

Bit's impossible to secure a contract against receiving ether, because selfdestruct will always send ether to the address in the argument. This is a design decision of the Ethereum platform.

Cselfdestruct doesn't send anything to a contract, it just re-assigns the owner of the contract to a new person. Sending ether must be done outside of selfdestruct.

Answer : B

Question 4

If you need more fine-grained functionality than solidity offers out of the box:

Ayou can incorporate inline-assembly to get better controls.

Byou have to import pre-compiled assembly files which are then hard-copied into the bytecode of the compiled solidity file.

Cyou can use Viper, the experimental assembly like language specifically to offer more flexibility.

Answer : A

Question 5

The nonce-field in a transaction is used:

Ato protect against replay attacks.

Bto have an additional checksum for transactions.

Cto sum up all ethers sent from that address.

Answer : A

Question 6

You interact with a smart contract and see a gas usage of 50,000 gas with a gas cost of 15Gwei.

How much Ether would you have to pay to the miner?

A750,000,000,000,000 Wei

B750,000,000,000 Wei

C750,000,000 Wei

DA flat fee of 1 Ether

Answer : A

Question 7

The Fallback function:

Acannot receive Ether, not even by adding the payable modifier.

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

Ccan be used to avoid receiving ether.

Answer : B

Blockchain BTA Certified Blockchain Developer - Ethereum CBDE Exam Practice Test