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: paleontologists study the remains of plants. 
Question: What do palentologists study?
plants.

Fact: Earthworm burrows help aerate soil, which is essential for growing plants. 
Question: Earthworm burrows help aerate soil, which is essential for what?
growing plants.

Fact: hormones control heart rate. 
Question: What do hormones control?

Heart rate.