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: heat is detected by sensory nerve cells. 
Question: What is detected by sensory nerve cells?
heat.

Fact: cattle can have a negative impact on the environment. 
Question: what can have a negative impact on the environment?
cattle.

Fact: an image in a mirror is formed by reflecting photons. 
Question: When a mirror reflects photons it creates?

an image.