TASK DEFINITION: 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.
PROBLEM: Question: What is the key to the demographic transition? Answer: reduced family size

SOLUTION: Reduced family size is the key to the demographic transition.

PROBLEM: Question: A binary molecular compound is made up of two of what? Answer: elements

SOLUTION: A binary molecular compound is made up of two elements.

PROBLEM: Question: Frogs are amphibians that live part of the time in fresh water and rest of the time where? Answer: on land

SOLUTION:
Frogs are amphibians that live part of the time in fresh water and live rest of the time on land.