Blockchain CBDE Exam Questions Instant Access

Question 1

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

Athe User.

Bcontract A.

Answer : B

Question 2

Proof of Work (PoW) vs. Proof of Stake.

APoW is computationally intensive which requires lots of energy. On the other hand, miners earn straightforward a reward for mining a block and incorporating transactions.

BPoW is better than PoS, because with PoS we increase the amount of energy spent on the network.

CPoS is mining with specialized new hardware that has to be purchased with a stack of Ether in the network. Hence the Name: Proof of Stake, which derives from Stack.

Answer : A

Question 3

When considering smart contracts and the blockchain it's good:

Ato move all existing logic to the blockchain, so everything runs on the same system. This way it might be more complex, but easier to maintain.

Bto move only those parts to the blockchain that really need the blockchain. This way smart contracts can be easier to read, easier to test and are not so complex.

Cto move those parts to the blockchain that deal with Ether transfers. All other parts can remain in traditional database systems. This way only the value-transfer is on the blockchain.

Answer : B

Question 4

Finish the sentence: The Library Web3.js is ...:

Auseful when developing distributed applications with HTML and JavaScript, because it already implements the abstraction of the JSON-RPC interface of Ethereum Nodes.

Bnecessary when developing distributed applications with HTML and JavaScript, because the proprietary JSON-RPC interface of Ethereum Nodes is a closed source.

Answer : A

Question 5

Solidity files:

Acan't be split across multiple files, everything should be in one single file.

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

Ccan 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';'.

Answer : C

Question 6

Function and Variable Visibility:

Aa function that is marked as internal cannot be called by other contracts, unless the function is used by a derived contract. Private Functions cannot be called by any other outside contract and public variables are generating automatically a getter function.

Ba function that is marked as external can never be called internally. Private functions can also be called by derived contracts using inheritance. Private variables are accessible also in derived contracts.

Answer : A

Question 7

Truffle:

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

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

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

Answer : A

Blockchain BTA Certified Blockchain Developer - Ethereum CBDE Exam Questions