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Blockchain CBDE BTA Certified Blockchain Developer - Ethereum Exam Practice Test

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Total 102 questions

BTA Certified Blockchain Developer - Ethereum Questions and Answers

Question 1

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

Options:

A.

to 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.

B.

to 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.

C.

to 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.

Question 2

Public Keys vs. Private Keys. Which statement is true?

Options:

A.

The Public Key is for Signing Transactions, the Private Key must be given out to verify the signature.

B.

The Private Key signs transactions, the Public Key can verify the signature.

C.

The Private Key is to generate a Public Key. The Public Key can sign transactions, the address is here to verify the transactions.

Question 3

Which statement is true about the EVM?

Options:

A.

While the EVM is Sandboxed, it isn't as powerful as the Bitcoin Network, because it's not Turing Complete.

B.

The EVM can't access hardware layers or anything outside a blockchain node because it's sandboxed.

C.

The EVM is extremely powerful, turing complete and perfect for doing computational intensive things, because of the direct access to the graphics card.

Question 4

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

Options:

A.

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

B.

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

C.

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

Question 5

Block Difficulty:

Options:

A.

is determined by the Ethereum Committee every fortnight to reflect the average amount of transaction and it cannot be influenced by the network itself.

B.

increases when the time between mined blocks is below 10 seconds, while it decreases when the time is above 20 seconds.

C.

increases when the time between mined blocks is below 20 seconds, while it decreases when the time is above 60 seconds.

Question 6

Address.send() and address.transfer() are considered:

Options:

A.

safe against reentrancy because of the small gas stipend of 2300 gas.

B.

dangerous because they send all gas along, it's better to use address.call.value()().

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:

Options:

A.

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

B.

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

Question 8

Address.call.value():

Options:

A.

sends the gas stipend of 2300 gas and returns a false on error.

B.

sends all the gas along and cascades exceptions.

C.

sends all the gas along and returns a false on error.

D.

sends the gas stipend of 2300 gas and cascades exceptions.

Question 9

.Require is used:

Options:

A.

to check internal states that should never happen.

B.

to check input arguments from users.

Question 10

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 11

A Private Network is:

Options:

A.

a side Channel to the Ethereum Main Net which costs less gas to run smart contracts.

B.

an exact clone of the Rinkeby Test-Network which can be started as virtual machine in the Azure Cloud.

C.

a Network running only in a private area, where people cannot join freely and openly.

Question 12

Using truffle-contract over Web3.js:

Options:

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.

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

Externally Owned Accounts (EoA):

Options:

A.

are changing their address every time a Transaction is sent because of the nonce.

B.

are keeping their address, but on the blockchain a nonce is increased every time they send a transaction to avoid replay attacks.

Question 15

Ethereum Nodes:

Options:

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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Total 102 questions