Answer:
respiratory system
Explanation:
The bronchi become smaller the closer they get to the lung tissue and are then considered bronchioles. These passageways then evolve into tiny air sacs called alveoli, which is the site of oxygen and carbon dioxide exchange in the respiratory system.
Answer:
D
Explanation:
I am working on that kind of stuff right now
Parietal cells within the stomach lining secrete hydrochloric acid that lowers the pH of the stomach. A low pH (1.5 to 2) activates pepsin. Acetylcholine, gastrin, and histamine stimulate the proton pump in parietal cells to release hydrogen ions and decrease pH.