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.

Q: Fact: conserving water can be used for survival in a desert. 
Question: Where is conserving water useful for survival?

A: desert.
****
Q: Fact: Vertebrates have a complete digestive system and a closed circulatory system. 
Question: vertebrates have a complete digestive system and a what?

A: closed circulatory system.
****
Q: Fact: gravity causes objects that have mass to be pulled down on Earth. 
Question: where does gravity cause an object to be pulled down to?

A:
Earth.
****