Question

the normal level at which a physiological variable is maintained is known as a stimulus b control center c effector d set point

Explanation:

In physiological regulation, the set - point is the normal level at which a physiological variable is maintained. A stimulus can cause a deviation from the set - point, the control center processes information and sends signals to the effector which acts to bring the variable back to the set - point.

Answer:

D. set point