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  • Exam Name: BTA Certified Blockchain Developer - Ethereum
  • Last Update: Jul 16, 2024
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CBDE Practice Exam Questions with Answers BTA Certified Blockchain Developer - Ethereum Certification

Question # 6

It’s possible to access the blockchain via an Ethereum Node:

A.

only via JavaScript because there is the proprietary Web3.js library.

B.

by any programming language, as long as it adheres to the JSON-RPC standard.

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Question # 7

View and Pure Functions:

A.

can only be accessed during calls.

B.

can be accessed during transactions and calls.

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Question # 8

You interact with a smart contract and see a gas usage of 50,000 gas with a gas cost of 15Gwei.

How much Ether would you have to pay to the miner?

A.

750,000,000,000,000 Wei

B.

750,000,000,000 Wei

C.

750,000,000 Wei

D.

A flat fee of 1 Ether

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Question # 9

Using truffle-contract over Web3.js:

A.

is a must for every developer, because Web3.js changes so often.

B.

is a convenient way because Web3.js is currently still in beta and truffle-contract can handle transactions with JavaScript-promises.

C.

they are both completely different things. Truffle-Contract is a framework while Web3.js is a library.

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Question # 10

Address.Call vs. Address.Delegatecall:

A.

Address.call() is used for calling other contracts using the scope of the called contract in terms of storage variables. Address.delegatecall() is used for libraries, which uses the storage variables of the contract who called. Libraries are a great way to re-use already existing code and delegatecall can make sure that no storage is used from the library, instead it looks like the code is directly copied into the calling contract.

B.

Address.delegatecall() is used for calling other contracts using the scope of the called contract in terms of storage variables. Address.call() is used for libraries, which uses the storage variables of the contract who called. Libraries are a great way to re-use already existing code and call() can make sure that no storage is used from the library, instead it looks like the code is directly copied into the calling contract.

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Question # 11

The nonce-field in a transaction is used:

A.

to protect against replay attacks.

B.

to have an additional checksum for transactions.

C.

to sum up all ethers sent from that address.

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Question # 12

Ethereum Nodes:

A.

must implement the Ethereum protocol and external access can only be done via the proprietary Ethereum Libraries like Web3.js.

B.

must implement the Ethereum Protocol and a JSON-RPC to talk with clients.

C.

must implement Web3.js to interact with Websites.

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Question # 13

All low-level functions on the address, so address.send(), address.call.valueQQ, address.callcode and address.delegatecall:

A.

are interrupting execution on error, because they throw an exception.

B.

continuing execution on error silently, which is the reason why they are so dangerous.

C.

returning Booleans to indicate an error during execution.

D.

.send() throws an exception, while the other functions are returning Booleans during execution to indicate an error.

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Question # 14

On a consortium network:

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.

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Question # 15

It's not possible to use inheritance from multiple sources in Solidity.

A.

True

B.

False

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Question # 16

For Rapid Development Cycles it's good:

A.

to deploy to the main-network as quickly as possible.

B.

to use in-memory blockchain simulations, because mining works instantaneously.

C.

to use a private network at all times, because this is the closest you get to the real network.

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Question # 17

When a new block is mined:

A.

a list of transactions as well as uncles is incorporated in the block. All gas that is used during those transactions is added to the miners' balance. Also, the block reward is added to the miner. Then the same transactions are run again by every participating node in the network to achieve consensus.

B.

a list of transactions is incorporated in that block. Gas used during the execution is attached to the executing contracts while the block reward is automatically spread across the mining pool to ensure a fair spread. Consensus is reached by a special form of hash code.

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Question # 18

Block Timestamp:

A.

the timestamp is based on the time zone of the miner, that is why it changes the difficulty continuously to reflect network latency.

B.

the timestamp can't be influenced by a miner and is generally considered safe to be used for randomness on the blockchain.

C.

the timestamp can be influenced by a miner to a certain degree but it's always independent from the time-zone.

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Question # 19

Why is it important to follow the same Interfaces?

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.

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Question # 20

Which is the right order for Denominations?

A.

Wei, Finney, Szabo, Ether, Tether.

B.

Finney, Szabo, Mether, Gwei.

C.

Gwei, Szabo, Finney, Ether.

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Question # 21

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

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.

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Question # 22

If you are starting a new ERC20 token:

A.

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

B.

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

C.

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

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Question # 23

What are Ethereum Nodes?

A.

Programs implementing the Ethereum Protocol to talk to each other and JSON-RPC interfaces to talk to the outside world.

B.

A Java-Script library to compile and run Solidity Code.

C.

A Framework for deploying and running smart contract in a decentralized way.

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Question # 24

Loops in Solidity:

A.

are a great way to circumvent gas requirements, because a loop will only consume gas once.

B.

are dangerous when used with data structures that grow, such as arrays or mapping, because it is hard to estimate the gas requirements.

C.

should be avoided where possible, because of unknown side-effects on the gas requirements.

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Question # 25

The Fallback function:

A.

cannot receive Ether, not even by adding the payable modifier.

B.

can contain as much logic as you want, but it’s better to keep it short and not exceed the gas stipend of 2300 gas.

C.

can be used to avoid receiving ether.

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Question # 26

A Hashing Algorithm is deterministic. What does it mean?

A.

it always produces the same output given the same input.

B.

it uses equally distributed data to produce the output given a long input.

C.

it shouldn't be possible to re-generate the input given the output.

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Question # 27

A version pragma is a great way to make it clear:

A.

for which compiler version a smart contract was developed for. It helps to avoid breaking changes.

B.

for which blockchain a smart contract was developed for. It helps to avoid confusion with beta-customers.

C.

for which blockchain node a smart contract was developed for. It helps to avoid mixing up different versions of go-ethereum.

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Question # 28

What are Private Keys used for?

A.

To Protect the Public Keys by being cryptographically significant.

B.

To Sign Transactions And To Derive an Address From.

C.

To Generate An Address which can sign transactions.

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Question # 29

When using assert to check invariants and it evaluates to false:

A.

all gas is consumed.

B.

all remaining gas is returned.

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Question # 30

Solidity files:

A.

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

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 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';".

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