Question

carbon that is underground in the form of fossilized animals cannot be used in the carbon cycle unless humans extract it from the ground. when an element is stored in a part of the carbon cycle, what do we call it?
gone forever
a nutrient sink

Explanation:

A nutrient sink is a part of the carbon cycle where carbon (or other elements) is stored. In the carbon cycle, when carbon is stored in a particular reservoir (like underground as fossilized animals in this case), it is called a nutrient sink. "Gone forever" is incorrect as carbon in such sinks can be re - entered into the cycle (e.g., through human extraction and combustion).

Answer:

a nutrient sink