Hydrochloric acid (HCI) is secreted from?

A. Chief cells; hydrochloric acid (HCl); parietal cells: Pepsinogen is produced by chief cells, and it is activated into pepsin by hydrochloric acid (HCl) secreted by parietal cells.

B. Chief cells; carbonic anhydrase (CAH); parietal cells: Chief cells produce pepsinogen, but it is not activated by carbonic anhydrase. Instead, it is activated by HCl.

C. Parietal cells; carbonic anhydrase (CAH); chief cells: Pepsinogen is produced by chief cells, not parietal cells, and its activation involves HCl, not carbonic anhydrase.

D. Parietal cells; hydrochloric acid (HCl); chief cells: Pepsinogen is produced by chief cells, not parietal cells, and is activated by HCl.

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.