PoS:

A. would be better, because it can reduce the amount of energy needed for mining.

B. would be worse, because it would increase the amount of energy needed for mining.

If a User calls contract A and that calls Contract B, then msg.sender in Contract B will contain the address of:

A. the User.

B. contract A.

If contract MyContractA is derived from Contract MyContractB, then this would be the right syntax:

A. contract MyContractA is MyContractB { … }

B. contract MyContractA inherit (MyContractB) {…}

C. contract MyContractA extends MyContractB {…}

D. contract MyContractB derives MyContractA {…}

Block Timestamp:

A. the timestamp is based on the time zone of the miner, that is why it changes the difficulty continuously to reflect network latency.

B. the timestamp can't be influenced by a miner and is generally considered safe to be used for randomness on the blockchain.

C. the timestamp can be influenced by a miner to a certain degree but it's always independent from the time-zone.

A Struct is a great way:

A. to define a new datatype in Solidity, so you don't need to use objects of another contract.

B. to hold instances of other contracts.

C. to implement pointers to other contracts that can hold new datatypes.

DApps are:

A. great, because they cut the middle man, run on a trusted platform, apply logic to the blockchain where already economic assets are running and thus allow peer to peer trade.

B. an amazing way to create new applications. Those applications run entirely separated from other applications on the platform and allow for logical interactions. They can't access any funds to add an additional layer of trust.

C. a new way of applying logical operations for banks and big financial institutions. This way they can reduce the staff while operating at increased security.

To send ether to a contract without a function call:

A. a fallback function must be declared and it must be made payable. If there is no fallback function or the fallback function is not payable it will throw an exception.

B. either a fallback function which is payable exists, or no fallback function at all exists.

C. you cannot send ether to a contract without explicitly calling a function. The fallback function can never receive ether.

When a smart contract pays out money:

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.

A Mapping consists of keys and value.

A. the Keys can be anything, but the value can't be another mapping or struct.

B. the Value can be anything, but the key cannot be another mapping, struct, integer or Boolean.

C. the value can be anything, but the key cannot be another mapping, struct, enum or dynamically sized array.

On a consortium network:

A. everybody can become a miner, everybody can send transactions and everything is public.

B. usually only a few selected nodes can be miners. Transactions can be further limited.

With the truffle config file you can manage:

A. the amount of gas your contract deployment and transactions, against your contract, will need. This way you can essentially lower the gas costs over traditional web3.js dApps.

B. different Networks to deploy your contracts to. This way you can easily deploy to a local blockchain, the main-net or the Ropsten/Rinkeby Test-Net with only one parameter.

C. you can manage your secret API keys to the Ethereum Network. This way you can get access to several different Ethereum nodes at the same time without the need to switch your keyfiles.

GETH:

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.