Answer: The correct answer is-
C. Insulin secretion in response to high blood sugar.
D. Increased heart rate in response to exercise.
F. Proton pumping to maintain a proper pH level.
Homeostasis can be described as a tendency of living organisms to maintain a state of stable internal environment. In other words, it is the tendency to resist any change in the optimal conditions for survival.
It is brought by several regulatory mechanisms in the body such as regulation of body temperature, regulation of pH, regulation of osmolarity etc.
Thus, option C), D), and F) are the examples of feedback mechanisms that help in maintaining homeostasis.