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: male dogs use natural aphrodisiacs in urine to mark their territory. 
Question: what do male dogs use in their urine to mark their territory?
natural aphrodisiacs.

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: When one solvent reacts with another, chemical bonds form. 
Question: What is it called when one solvent combines with another, what forms?

chemical bonds.