CBDE Online Practice Questions and Answers

What's the correct scientific notation?

A. 1 Ether = 10^18 wei, 10^9 Gwei, 10^3 Finney

B. 1 Ether = 10^19 wei, 10^13 Gwei, 10^3 Finney

C. 1 Ether = 10^16 wei, 10^13 Gwei, 10^3 Finney

D. 1 Ether = 10^18 wei, 10^6 Gwei, 10^6 Finney

PoS:

A. would be better, because it can reduce the amount of energy needed for mining.

B. would be worse, because it would increase the amount of energy needed for mining.

For Rapid Development Cycles it's good:

A. to deploy to the main-network as quickly as possible.

B. to use in-memory blockchain simulations, because mining works instantaneously.

C. to use a private network at all times, because this is the closest you get to the real network.

Go-Ethereum vs. Ganache:

A. both are the same, just implemented in a different language.

B. with Go-Ethereum you get a real blockchain node where you can create your own local private network, connect to Test-Networks or the Main-Net, while with Ganache you get an in-memory blockchain simulation.

C. with Ganache you get a real blockchain node where you can connect to the Test-Networks Rinkeby and Ropsten.

GETH:

A. is the reference implementation of the Ethereum protocol and every other node implementation internally uses the closed-source from Geth.

B. is the library that is used for the blockchain node Go-Ethereum. It is also used by Parity is parts, because it's closed source.

C. is one of the many blockchain nodes that implement the Ethereum Protocol. It's open source and everyone can contribute.

Importing from GitHub:

A. works across all compilers and platforms the same way.

B. is generally possible, but currently works only in Remix, but doesn't work in Truffle.

Multi-Line Comments in Solidity are:

A. working with either // or ///

B. working with /* comment */ or /** @.. natspec style */

C. not possible, all comments must be single-line.

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.

If contract MyContractA is derived from Contract MyContractB, then this would be the right syntax:

A. contract MyContractA is MyContractB { ... }

B. contract MyContractA inherit (MyContractB) {...}

C. contract MyContractA extends MyContractB {...}

D. contract MyContractB derives MyContractA {...}

When a smart contract pays out money:

A. it's good to use a push over a pull method.

B. it's good to use a push and a pull method to ensure that participants can get their money no matter the contract state. In addition to and pushing it should contain a withdraw method.

C. it's good to use only pull and no push method.