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: Roots will decay is the conditions for growth aren't favorable. 
Question: What will decay is the conditions for growth aren't favorable?
answer:
roots.


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


question:
Fact: Some invertebrates have shells. 
Question: Some invertebrates may have which feature?
answer:

shell.