What does it mean for a module to be ""coherent?"" Why is this important? What are the advantages of coherence? What are the disadvantages of incoherent modules?

Following are the answer to this question:

Explanation:

Coherent means, in some kind of a communication process,  that transmits the side and well the receiver side generally use those common features, which is the provider used for modulation.  

Its frequency only at the end and end of both the transponder is the same.  

It's also important to recover from the modulated signal to its original message signal.

The advantage of coherence clarifies the system architecture and signal transmission throughout the carrier, as well as the carrier, is not to be regenerated on the receiver side.  The disadvantage of the incoherent modules is being more difficult to build than the Coherent modules.

Answer made of magnesium alloy;

The answer for your specific question is d.