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Blockchain CBDE BTA Certified Blockchain Developer - Ethereum Exam Practice Test

Demo: 15 questions
Total 102 questions

BTA Certified Blockchain Developer - Ethereum Questions and Answers

Question 1

Address.send():

Options:

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.

Question 2

Consensus is reached:

Options:

A.

by the miner nodes which make sure that a transaction is valid.

B.

by every single node in the blockchain network executing the same transaction.

C.

by a cryptographic secure signature algorithm called ECDSA which makes sure that cheating is impossible.

Question 3

When solidity is compiled then also Metadata is generated:

Options:

A.

the 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.

B.

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

C.

the 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.

Question 4

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

Options:

A.

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

B.

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

C.

PoS 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.

Question 5

If you need more fine-grained functionality than solidity offers out of the box:

Options:

A.

you can incorporate inline-assembly to get better controls.

B.

you have to import pre-compiled assembly files which are then hard-copied into the bytecode of the compiled solidity file.

C.

you can use Viper, the experimental assembly like language specifically to offer more flexibility.

Question 6

Assert is used:

Options:

A.

to check internal states that should never happen.

B.

to check input arguments from users.

Question 7

Smart Contracts:

Options:

A.

are always living on the same address, because the blockchain is deterministic. So, one account can always have one smart contract.

B.

are having the same address as the EOA.

C.

are sitting on their own address. The Address is created from the nonce and the EOA address and could be known in advance before deploying the smart contract.

D.

the address of the smart contract is a random address which gets generated by the miner who mines the contract-creation transaction.

Question 8

Solidity gets compiled:

Options:

A.

to bytecode that can't be understood by humans.

B.

to bytecodes which are essentially opcodes running instruction by instruction.

Question 9

Single line comments in Solidity are:

Options:

A.

working with either // or ///

B.

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

C.

not possible, all comments must be multi-line.

Question 10

On a consortium network:

Options:

A.

everybody can become a miner, everybody can send transactions and everything is public.

B.

usually only a few selected nodes can be miners. Transactions can be further limited.

Question 11

Why is it important to follow the same Interfaces?

Options:

A.

Websites 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.

B.

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

Question 12

A Mapping consists of keys and value.

Options:

A.

the Keys can be anything, but the value can't be another mapping or struct.

B.

the Value can be anything, but the key cannot be another mapping, struct, integer or Boolean.

C.

the value can be anything, but the key cannot be another mapping, struct, enum or dynamically sized array.

Question 13

When a smart contract pays out money:

Options:

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.

Question 14

According to the official Style Guide:

Options:

A.

you should capitalize function names, events and contract names, to avoid confusion with JavaScript. You should use Tabs to indentation and a maximum of 80 characters per line.

B.

contract names should be capitalized, while functions should be mixedCase. You should use 4 spaces as indentation and a maximum of 79 (or 99) characters per line.

C.

contract should be mixedCase, as well as function names. Events should be capitalized. 2 spaces should be used as indentation and a maximum of 120 characters per line.

Question 15

Unit-Testing on a local chain is important, because it helps you:

Options:

A.

to run tests quickly and especially for free, compared to continuous deployment on the MainNetwork. This way you save a lot of fees, time and costs.

B.

to run tests in an environment where logging is activated. On the Main-Net you have no access to transaction logs and this is ultimately the information you need to debug your contracts.

C.

to avoid regression bugs with contracts that are updated constantly on the main-net. Once you update a contract on the main-net, the address stays the same, but the code changes and this can have disastrous side-effects.

Demo: 15 questions
Total 102 questions