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.
One example: Fact: pesticides can harm animals. 
Question: What can harm animals?
Solution is here: pesticides.
Explanation: The answer is present in the span of the fact.

Now, solve this: Fact: some larvae lack a hardened backbone. 
Question: What do some larvae lack?
Solution:
hardened backbone.