Blockchain CBSA Practice Test - Questions Answers, Page 3
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Question 21

The gas price is a value set by the creator of the blockchain transaction? Select best answer.
Explanation:
The gas price is a value set by the creator of the transaction, who has to pay gas_price * gas up front from the sending account. If some gas is left after the execution, it is refunded in the same way. If the gas is used up at any point (i.e. it is negative), an out-of-gas exception is triggered, which reverts all modifications made to the state in the current call frame.
Reference: https://solidity.readthedocs.io/en/latest/introduction-to-smart-contracts.html#the-ethereum-virtual-machine
Question 22

R3 Corda does not organize time into blocks. What does Corda actually perform and use?
Explanation:
Review Technical Whitepaper https://www.corda.net/ Corda network has one or more notary services which provide transaction ordering and timestamping services, thus abstracting the role miners play in other systems into a pluggable component.
Question 23

Contracts live on the blockchain in an Ethereum-specific binary format called _____________?
Explanation:
The Ethereum Virtual Machine (EVM) is the runtime environment for smart contracts in Ethereum. It is not only sandboxed, but actually completely isolated, which means that code running inside the EVM has no access to network, filesystem, or other processes. Smart contracts even have limited access to other smart contracts.
Question 24

Bitcoin uses what proof of work consensus system?
Explanation:
Bitcoin uses the Hashcash proof of work system.
Reference: https://en.bitcoin.it/wiki/Hashcash
Question 25

An _____________ is a well-known service that signs transactions if they state a fact and that fact is considered to be true. They may optionally also provide the facts.
Explanation:
An oracle is a well known service that signs transactions if they state a fact and that fact is considered to be true. They may also optionally provide the facts r 3 Corda Technical Whitepaper.
Question 26

Select the two kinds of accounts in Ethereum which share the same address space. (Select two.)
Question 27

The most popular Ethereum development framework is currently Truffle.
What are three features of Truffle? (Select three.)
Explanation:
Truffle is a development environment, testing framework and asset pipeline for Ethereum, aiming to make life as an Ethereum developer easier. Reference:
https://github.com/trufflesuite/truffle
Question 28

You are considering writing smart contracts and there are a few different languages you can consider. (Select two.)
Explanation:
To write smart contracts there are a few different languages: Solidity, which is like JavaScript and has .sol as a file extension, Serpent, Python-like with extension .se, and a 3rd, LLL, based on Lisp. Serpent was popular a while back but Solidity is the most popular right now and more robust, so just use Solidity. You prefer Python? Use Solidity.
Reference: https://medium.com/@ConsenSys/a-101-noob-intro-to-programming-smart-contracts-on-ethereum-695d15c1dab4
Question 29

Satoshi Nakamoto invented a way to achieve Decentralized Consensus?
Explanation:
Reference: https://www.interlogica.it/en/insight-en/nakamoto-consensus/
Question 30

Which of the following would NOT be true about what a smart contract gives your organization?
Explanation:
Smart contracts generally are not legal contracts. However, its possible that a smart contract could be accepted as a legal contract but not normally. Read more about Smart contracts here Reference: https://blockgeeks.com/guides/smart-contracts/
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