Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

Q: Question: What does rising air do when it reaches the top of the troposphere? Answer: cools

A: The rising air cools as it reaches the top of the troposphere. The air gets denser, so it sinks to the surface. The sinking, heavy air creates an area of high air pressure near the ground.
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Q: Question: What types of glands do only female mammals have? Answer: mammary

A: Two traits are used to define the mammal class. They are fur or hair and mammary glands in females.
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Q: Question: Supercontinents have formed at least how many times in earth history? Answer: five

A:
The first continents were small but they grew over time. Supercontinents have formed at least five times in Earth history.
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