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.

Example Input: Question: What is the key to the demographic transition? Answer: reduced family size
Example Output: Reduced family size is the key to the demographic transition.

Example Input: Question: Where does the stratosphere get most of its heat? Answer: sun
Example Output: Sun does the stratosphere get most of its heat.

Example Input: Question: Ions that contain fewer electrons than protons have a net positive charge and are called what? Answer: cations
Example Output:
Ions that contain fewer electrons than protons have a net positive charge and are called cations.