CBDE Online Practice Questions and Answers

A Blockchain Node:

A. can never become a mining node.

B. can always become a mining node.

C. can become a mining node, depending if the implementation has the functionality implemented.

EVM assembly:

A. is much better than Solidity and a viable alternative.

B. can be split across multiple files, but every contract must be in a file with the same name as the contract itself.

C. is another language similar to LLL, more secure than Solidity.

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.

Variables of the type address store:

A. a 20 bytes value

B. a 32 bytes value

C. a string

D. a 20 characters long hex number

Why is it important to follow the same Interfaces?

A. Websites that try to interface with the Token would have to know the exact ABI. It is upfront clear how the interaction has to be with the standard Interfaces.

B. The Ethereum Foundation can easily validate the Tokens and approve any audits by following the standard interface.

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

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

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

C. returning 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.

When using require to check input parameters and it evaluates to false:

A. all gas is consumed

B. all remaining gas is returned.

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

A. you can incorporate inline-assembly to get better controls.

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

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

Truffle:

A. is a framework that helps developers with Testing, Deployment and Management of Smart Contracts and Distributed Applications.

B. is a library that helps developers to connect to Ethereum nodes, because it abstracts the JSONRPC interface.

C. is a framework for Java, similar to Web3.js for JavaScript. It's a great way to develop distributed Java enterprise applications.

Truffle has an integrated in-memory blockchain which makes unit-testing very easy:

A. True, but it's still good to use Ganache, or even a real private network for testing.

B. False, it's necessary to use Ganache or even a real private network for testing.