All cells contain a phosphate buffer system within their internal fluid to maintain a constant ph. this system can be summarized by the following chemical equation: h2po4- (aq) h+ (aq) + hpo4-2 (aq) this system mostly contributes to which of the following cellular activities a. maintaining homeostasis b. reproduction c. natural selection d. acquiring energy

The correct answer is A. maintaining homeostasis.
Homeostasis is a term referring to an organisms continuous process of maintaining and auto-regulating the conditions of its internal environment. Variables such as pH, temperature, and fluid balance need to be at optimal conditions in order for the organism to function properly.
In this example, the phosphate buffer system permits the organisms to maintain a constant pH in their intracellular fluid. This is one of the organism's homeostatic mechanisms.