Plants use carbon dioxide in a process known as photosynthesis. During photosynthesis, plants give off oxygen as a waste product. Carbon dioxide moves from the air into the leaves of plants through tiny openings in the plant's leaves. Oxygen moves out of the plant leaf through these same openings.
I may be wrong but I think the answer is Photosynthesis.
Bacteria can convert nitrogen in the air into a form plants can use
I think the correct answer from the choices listed above is option C. The function that is both performed by goblet cells and lacrimal glands is protection. They produce mucus in order to protect mucous membranes. Hope this answers the question.