Women have a tendency to retain water during part of the menstrual cycle because estrogen mimics the action of what?

A. Trypsin functions in the small intestine, where the environment is slightly alkaline. Therefore, this enzyme does not function at a low pH.

B. Pancreatic amylase also functions in the small intestine, where the pH is neutral to slightly alkaline.

C. Pepsin functions in the stomach, where the environment is highly acidic (pH 1.5 to 2). Pepsin is the correct answer because it works optimally at this low pH.

D. Salivary amylase functions in the mouth, where the pH is neutral or slightly alkaline.

A. The bicarbonate, phosphate, and protein: The major chemical buffer systems in the body are the bicarbonate buffer system, the phosphate buffer system, and the protein buffer system. These buffers help maintain pH balance in the blood and other fluids.

B. The urinary and digestive: The urinary and digestive systems are involved in excretion and digestion, not buffering.

C. The bicarbonate, nucleic acids, and protein: Nucleic acids are not major buffering systems in the body; the bicarbonate, phosphate, and protein systems are the primary ones.

D. The urinary and respiratory systems play roles in regulating acid-base balance through excretion and gas exchange but are not chemical buffer systems themselves.