Blockchain CBDE Exam Practice Test Instant Access

Question 1

If you are starting a new ERC20 token:

Ait would be best to start from scratch, just looking at the required interface.

Bit is beneficial to copy and paste the already existing code from the Ethereum wiki and modify this until you like it.

Cbest is to start with an audited implementation, for example from OpenZeppelin, in order to reuse already existing code.

Answer : C

Question 2

When solidity is compiled then also Metadata is generated:

Athe Metadata contains the ABI Array, which defines the Interface to interact with the Smart Contract. Metadata can also contain the address of the smart contract when it gets deployed.

Bmetadata contains the address, and the size of the smart contract. The ABI Array is generated externally upon deploying the smart contract.

Cthe ABI array and the Metadata are not generated when solidity is compiled to bytecode, its generated by a migration software which deploys the smart contract on the blockchain.

Answer : A

Question 3

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 4

Inheritance is useful, because a contract that is derived from another contract can make use of:

Aall public state variables and properties, public and internal functions and modifiers.

Ball public and private state variables, public, internal and external functions, but not modifiers

Call public state variables and properties, public functions and modifiers, but not internal, external or private ones.

Answer : A

Question 5

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

Acontract MyContractA is MyContractB { ... }

Bcontract MyContractA inherit (MyContractB) {...}

Ccontract MyContractA extends MyContractB {...}

Dcontract MyContractB derives MyContractA {...}

Answer : A

Question 6

Why is it important to follow the same Interfaces?

AWebsites 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.

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

Answer : A

Question 7

In order to implement an ERC20 token contract, you'd need at least to implement the following functions and events in order to fulfill the interface requirements:

AtotalSupply(), balanceOf(address), allowance(address,address), transfer(address,uint256), approve(address,uint256), transferFrom(address,address,uint256). Events: Transfer(address,address,uint256), Approval(address,address,uint256)

Bname(), symbol(), totalSupply(), balanceOf(address), ownerOf(uint26),approve(address,uint256), takeOwnership(uint256),transfer(address,uint256),Events: Transfer(address,address,uint256), Approval(address,address,uint256)

Answer : A

Blockchain BTA Certified Blockchain Developer - Ethereum Exam Practice Test