In this task, you are given a question and a corresponding answer. Your task is to generate a fact statement that is useful in answering the given question.

[Q]: Question: What's a good way to heat up inside after ice skating on a frozen lake? Answer: set fire to some natural gas.
[A]: natural gas is a source of heat by burning


[Q]: Question: What is a source of energy for animals? Answer: grains.
[A]: food is a source of energy for animals


[Q]: Question: the circulatory system carries oxygen from the digestive and respiratory systems to the rest of the what? Answer: physical being.
[A]:
the circulatory system carries oxygen from the digestive and respiratory systems to the rest of the body