Living things must maintain a fairly constant pH balance because the pH level determines Which on?

Which mantle is under the crust the upper mantle or the lower mantle i think it's upper let me know if i'm right

I’m doing some practice exam questions for biology, and i’m not sure how to do these 3 parts to the question.

The picture shows a location in india that is very dry and arid. notice the tall mountains in the background; you can find high amounts of vegetation on the other side of the mountains. which statement is most likely true for this area?