The answer is B.
Water in the form of vapor enter the atmosphere. The vapor accumulates in the atmosphere to form clouds. Once the clouds are heavy enough, the water in the form of droplets fall towards land or as rain. It could also be in the form of other precipitation such as snow or hail. As the sun hits the waters in the land, it causes the water to evaporate and the cycle continues.
I think is the first and second!!
Dehydration because animals can only live so long with water
I believe the answer is: Different scientists use different data for investigation.
I say that because different scientists have different equipment, ideas, and have different methods. I hope I was right and i hope it helped and i wasn't to late to answer this question.