instruction:
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.
question:
Fact: Mammals generate heat mainly by burning calories. 
Question: Mammals generate heat mainly by what?
answer:
burning calories.


question:
Fact: animals with calcite shells form large colonies in shallow tropical water. 
Question: Animals with _ form large colonies in shallow tropical water?
answer:
calcite shells.


question:
Fact: bladder infections can be treated with penicillin. 
Question: what can bladder infections be treated with?
answer:

penicillin.