___ molecules of water are needed to make one of molecule of glucose.

6Molecules Needed

Explanation:

For each molecule of glucose produced: 6 water water molecules are oxidized, and become the source of electrons for carbon dioxide reduction. 6 molecules of carbon dioxide are required, one for each carbon atom in glucose. 6 molecules of oxygen are produced as a by product of water oxidation

the correct answer is:

a population changes in response to a change in the environment.