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: muscles contain cells. 
Question: What do muscles contain?
answer:
cells.


question:
Fact: the planet being buried in snow and ice for millions of years at a time is relatively rare. 
Question: What is true about the planet being buried in snow and ice for millions of years at a time?
answer:
it is relatively rare.


question:
Fact: The formation of high mountains can be explained by the study of plate tectonics. 
Question: Plate tectonics can explain which natural occurance?
answer:

Mountain formation.