CBDE Practice Questions

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.

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.

A.  

with private state variables. This way nobody else other than the smart contract itself can see the information

B.  

with external contracts holding those values. This way we can make sure that the information flow is following a clear logic and nobody else can access this information.

C.  

You can't hide anything on the blockchain, because the information is public, just the call is private which means only other smart contracts would be limited in accessing that information.

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.

A.  

is the reference implementation of the Ethereum protocol and every other node implementation internally uses the closed-source from Geth.

B.  

is the library that is used for the blockchain node Go-Ethereum. It is also used by Parity is parts, because it's closed source.

C.  

is one of the many blockchain nodes that implement the Ethereum Protocol. It's open source and everyone can contribute.