Question 1

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.

Answer: A

Question 2

Smart Contracts can be written in:

Options :

A : Java, C++, Solidity and JavaScript, because the Ethereum Blockchain is completely language agnostic and cross compilers exist for every major language

B : Solidity, Viper, LLL and Serpent, because those are high level languages that are compiled down to bytecode.

C : Solidity and JavaScript, because those are the official first implementations for Distributed applications and the Blockchain supports those languages fully.

Answer: B

Question 3

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

Answer: B

Question 4

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

Options :

A : all gas is consumed.

B : all remaining gas is returned

Answer: A

Question 5

The Fallback function:

Options :

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

Answer: B

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