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.
Answer:
PVR is calculated by the formulae: 
Explanation:
Pulmonary vascular resistance may be defined as the resistance to blood through the pulmonary circulation.
PVR can be determined by the following formula:

Here, PAP is the pulmonary artery pressure, PAOP is pulmonary artery occlusion pressure and CO is cardiac output.
Answer:
The evolution of the peppered moth is an evolutionary instance of directional colour change in the moth population as a consequence of air pollution during the Industrial Revolution. ... Later, when pollution was reduced, the light-coloured form again predominated.