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: 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?
it is relatively rare.

Fact: rivers can slowly dissolve carbon in sedimentary rock. 
Question: what can slowly dissolve carbon in sedimentary rock?
rivers.

Fact: the gravitational pull of the Moon on Earth 's oceans causes water to rise and fall. 
Question: the gravitational pull of the Moon on Earth 's oceans causes water to what?

rise and fall.