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: fluid connective tissue carries oxygen. 
Question: What does fluid connective tissue carry?
oxygen.

Fact: Hummingbirds co-evolved with plants. 
Question: Hummingbirds are what they are today as a necessary consequence of their relationship to what?
Plants.

Fact: polar bears can generate little bursts of heat by shivering. 
Question: What can generate little bursts of heat by shivering?

polar bears.