According to cell theory, all new cells...
A. must share DNA with existing cells.
B. must eat.
C. come from other cells.

C. come from other cells.

Explanation:

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.