Modern classification, otherwise known as taxonomy, was invented so as to have a single system used throughout the entire world in understanding different types of beings in existence. This way you avoid having different names for same things.
I might be wrong but I think C ( what the wave it traveling through). I think C because a wave medium is the substance that carries a wave (or disturbance) from one location to another. The wave medium is not the wave itself and it doesn’t make the wave. It just Carries or transports the wave from its source to other locations.
The answer to this is a group of individuals many species living in an area.
Answer:
to area of high concentration to form a solution.