What's the correct scientific notation?

A. 1 Ether = 10^18 wei, 10^9 Gwei, 10^3 Finney

B. 1 Ether = 10^19 wei, 10^13 Gwei, 10^3 Finney

C. 1 Ether = 10^16 wei, 10^13 Gwei, 10^3 Finney

D. 1 Ether = 10^18 wei, 10^6 Gwei, 10^6 Finney

If we divide two integers: 5/2, the result is:

A. 2, because the decimal is truncated.

B. 3, because it's always rounded.

C. 2.5, because it's automatically converted into a float.

Variables of the type address store:

A. a 20 bytes value

B. a 32 bytes value

C. a string

D. a 20 characters long hex number

Truffle has an integrated in-memory blockchain which makes unit-testing very easy:

A. True, but it's still good to use Ganache, or even a real private network for testing.

B. False, it's necessary to use Ganache or even a real private network for testing.

Consensus is reached:

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.

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

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.

What is the difference between ERC20 and ERC721 Tokens in simple terms?

A. The tokens of a certain ERC20 symbol are all the same, the tokens of an ERC721 symbol are all different. So, ERC20 tokens are fungible, while ERC721 tokens are nonfungible.

B. The tokens of a certain ERC20 symbol are all different, the tokens of an ERC721 symbol are all the same. So, ERC20 tokens are non-fungible while ERC721 tokens are fungible.

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

A. all gas is consumed

B. all remaining gas is returned

The JSON-RPC Protocol:

A. is used to communicate between blockchain nodes.

B. is used to ensure safe communication between miners.

C. is a mean of dumping the blockchain data in a so-called consensus export.

D. is used to communicate between the blockchain node and externally running applications.

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.

Hashing Mining uses:

A. Keccack256 while internally to hash values it's easy to use the Dagger-Hashimoto to create a meaningful hash.

B. the Dagger-Hashimoto hashing while internally the EVM uses SHA256 which is an alias for Keccack256.

C. the Dagger-Hashimoto hashing while internally the EVM uses Keccack256 which is almost similar to SHA256, but has a different padding so produces different hashes.