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: animals with calcite shells form large colonies in shallow tropical water. 
Question: Animals with _ form large colonies in shallow tropical water?
calcite shells.

Fact: Fossil fuels can be formed by layers of sediment pushing down on decomposing algae. 
Question: What is a product of layers of sediment pushing down on decomposing algae over time?
Fossil fuels.

Fact: Some species of amphibians are fed once a week. 
Question: Some species of amphibians are fed when?

once a week.