The end of a river or stream is the

transition zone
mouth
source
headwater

The correct answer that would best complete the given statement above would be the second option. The end of a river or stream is the MOUTH. Some rivers end in a fan-shaped series of small creeks, that is called a "delta". Whereas, the beginning of the river is called is the "headwater". Hope this answers your question. 

The correct answer is option (C) Gray rabbits would be eliminated by predators.

Explanation:

Camouflage is an adaptation by organisms allowing them to blend with the environment. This helps them in surviving or escaping from their predators. It can be through coloration or developing a particular pattern or mimicry.

The example given above is a type of camouflage through concealing coloration. Concealing coloration includes having a fixed camouflage and changing the camouflage depending on the environment. Grey rabbits cannot exhibit camouflage as the backgroud is dark rocks and light stones. As a result, these rabbits are clearly visible to the predators and get elimiated by them.