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: many plants respond to the days growing shorter in September by going dormant. 
Question: when do plants respond to shorter days by going dormant?
September.

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

Fact: A bicycle is a vehicle that requires smooth surfaces. 
Question: What kind of surface does a bicycle require to ride on?

smooth.