Blockchain CBDE Exam Practice Test Instant Access

Question 1

To generate a random number:

Ait's good to use the block timestamp, as this is always different.

Bit's good to use the block hash as this is clearly always very different.

Cit's good to use the RANDAO smart contract.

Dit's not possible to have a random number in a deterministic environment such as the Ethereum blockchain.

Answer : C

Question 2

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

Question 3

What is the difference between ERC20 and ERC721 Tokens in simple terms?

AThe tokens of a certain ERC20 symbol are all the same, the tokens of an ERC721 symbol are all different. So, ERC20 tokens are fungible, while ERC721 tokens are non-fungible.

BThe tokens of a certain ERC20 symbol are all different, the tokens of an ERC721 symbol are all the same. So, ERC20 tokens are non-fungible while ERC721 tokens are fungible.

Answer : A

Question 4

What's the difference between Ethereum Request for Comments (ERC) and Ethereum Improvement Proposals (EIP)?

AERC are here to define standards for the usage of Ethereum. EIP are here to improve the Ethereum Protocol itself.

BERC are here to propose new distributed applications on top of the Ethereum layer, while EIP are here to improve existing mining software.

CERC are an open platform to discuss continuous forking of the Ethereum platform. Successful forks are then incorporated in the EIP for further voting by the Ethereum Consortium.

Answer : A

Question 5

When defining a new datatype:

Aits best to use a contract with public storage variables, so it can be used like a class.

Bit's best to use a struct, which is cheaper than deploying a new contract.

Cit's not possible to generate new datatypes in Solidity.

Answer : B

Question 6

Address.send():

Awill cascade exceptions and address.transfer() will return a false on error.

Bwill return false on error while address.transfer() will cascade transactions.

Answer : B

Question 7

Variables of the type address store:

Aa 20 bytes value

Ba 32 bytes value

Ca string

Da 20 characters long hex number

Answer : A

Blockchain CBDE BTA Certified Blockchain Developer - Ethereum Exam Practice Test