Write a correct answer to the given question based on its associated fact. Make sure that your answer is contained in the associated fact. Don't be creative and introduce any new word that is not mentioned in the associated fact! Remember that the associated fact has been rearranged to form the question. So, the correct answer words must lie within the associated fact. The correct answer can be a word, phrase, or even a sentence.

Fact: Food is used for energy by the cells of most organisms. 
Question: Food is used for energy by what part of most organisms?
Cells.

Fact: animals cannot make their own food. 
Question: What cannot make their own food?
animals.

Fact: Reefs form in shallow tropical water. 
Question: What forms in shallow tropical water?

reefs.