When ATP Releases Some Energy, It Also Releases Inorganic Phosphate

Multiple Choice

When ATP releases some energy, it also releases inorganic phosphate. What purpose does this serve (if any) in the cell?

A) It is released as an excretory waste.
B) It can only be used to regenerate more ATP.
C) It can be added to water and excreted as a liquid.
D) It can be added to other molecules in order to activate them.
E) It can enter the nucleus to affect gene expression.