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: Energy enters ecosystems from the sun. 
Question: The sun contributes what to ecosystems?
answer:
energy.


question:
Fact: Water must not be polluted to be safe. 
Question: What can happen to water to make it unsafe?
answer:
Pollution.


question:
Fact: Water rises with flooding. 
Question: What happens when the water level rises?
answer:

flooding.