Online Access Free CBDE Practice Test

Integrating the community into your testing:

• A.is great, because they often find bugs which weren't considered before.
• B.is not good, because you might give out secrets.

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.

Solidity files:

• A.can be spread across multiple files. To import all contract from a file you can use "import 'myfile.sol'. To import Contract MyContract from myfile.sol you use "import {MyContract as SomeContract} from 'myfile.sol';".
• B.can be split across multiple files, but every contract must be in a file with the same name as the contract itself.
• C.can't be split across multiple files, everything should be in one single file.

With the truffle config file you can manage:

• A.the amount of gas your contract deployment and transactions, against your contract, will need. This way you can essentially lower the gas costs over traditional web3.js dApps.
• B.you can manage your secret API keys to the Ethereum Network. This way you can get access to several different Ethereum nodes at the same time without the need to switch your keyfiles.
• C.different Networks to deploy your contracts to. This way you can easily deploy to a local blockchain, the main-net or the Ropsten/Rinkeby Test-Net with only one parameter.

When a smart contract pays out money:

• A.it's good to use only pull and no push 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 a push over a pull method.