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: Which gas is given off by plants? Answer: Oxygen
[EX A]: Oxygen gas is given off by plants.

[EX Q]: Question: What do you call the hard case that surrounds the soft parts of some animals? Answer: exoskeleton
[EX A]: You call the hard case that surrounds the soft parts of some animals the exoskeleton.

[EX Q]: Question: Which theory explains how populations of organisms can change over time? Answer: evolution by natural selection
[EX A]:
Theevolution by natural selection theory explains how populations of organisms can change over time.