Lets use the process of elimination shall we?
It will not be A ,thats definetlyout because the word weathering is included, and weathering does not occur necessarily in a tropical forset
It will not be B because a tropical forest is full of rain and life.It is a very green place
D is totally out because in a tropical forest there are plenty of plants, and tropical fruits and animals
So its TOTALLY C!
C will be the answer because there is lots of rain in a rain forest, which causes soil to become nice and moist for plants!
Hope this helped!