The answer is B. They bring oxygen from the air into the body.
The lungs don’t produce or release oxygen so it’s not A. or D. The lungs do not transform oxygen into carbon dioxide cause our bodies need oxygen not carbon dioxide so it’s not C. Hope this helps!
IF YOUR ON PLATO THE ANSWER WOULD BE ..............C...........
If a major change in pH occurred, the protease enzymes would stop functioning or function very slowly, assuming the original pH was the most optimal pH for them.