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: preventing the transfer of energy from an organism's body causes it to keep warm. 
Question: what can preventing the transfer of cause the body to keep warm in an organism?

Answer: energy.


Question: Fact: Fossils are remnants of ancient life. 
Question: What ancient life remnants are studied?

Answer: fossils.


Question: Fact: Agnathans are thought to have been the earliest vertebrates. 
Question: What are Agnathans?

Answer:
vertebrates.