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: Fires, mainly caused by what, are a natural disturbance in temperate grasslands? Answer: lightning
[EX A]: Fires, mainly caused by lightning, are a natural disturbance in temperate grasslands.

[EX Q]: Question: To solubilize the fats so that they can be absorbed, what organ secretes a fluid called bile into the small intestine? Answer: gall bladder
[EX A]: To solubilize the fats so that they can be absorbed, the gall bladder secretes a fluid called bile into the small intestine.

[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.