In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.

[EX Q]: Question: What is the key to the demographic transition? Answer: reduced family size
[EX A]: Reduced family size is the key to the demographic transition.

[EX Q]: Question: When blood vessels in the head dilate, what kind of severe headache can occur? Answer: migraine
[EX A]: When blood vessels in the head dilate, a migraine, a severe headache, can occur.

[EX Q]: Question: What is the chemical formula for a glucose molecule? Answer: c6 h12 o6
[EX A]:
C6 h12 o6 is the chemical formula for a glucose molecule.