instruction:
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: Amphibians have a larynx to make sounds. 
Question: What do amphibians use to make sounds?
answer:
Voice box.


question:
Fact: Pollution is usually harmful to population size of a species. 
Question: What is usually harmful to the population size of a species?
answer:
Pollution.


question:
Fact: when intermediate length rays enter the eye through the pupil it falls on the retina. 
Question: what enters the eye through the pupil and falls on the retina?
answer:

intermediate length rays.