Biology

The correct answer is: C. The total amount of phosphorus on Earth is constant, but human activities can change its availability in ecosystems..

Here's why:

Phosphorus doesn’t enter or leave Earth’s system in significant amounts—it just cycles through rocks, water, soil, and living things. Human activities, like mining phosphate rock and using fertilizers, don’t create or destroy phosphorus, but they can move it around and make it more available (or cause pollution).

Why the other options are incorrect:
A. Human activities increase the total amount of phosphorus on Earth by adding fertili...