Earth’s atmosphere is a layer of gases—mostly nitrogen and oxygen—without which our planet would be in serious trouble. With this in mind, you can expect some questions on the GED Science test to cover this topic.

Practice Questions

Use the following information for both questions.

Earth’s atmosphere can be divided into several layers, including the troposphere, the stratosphere, the mesosphere and ionosphere, and the thermosphere. The temperature and altitude of each layer is listed in the following table.


  1. In which layer of the atmosphere do most humans live?

    A. troposphere B. stratosphere C. mesosphere and ionosphere D. thermosphere

  2. Which layer has the coldest average temperature?

    A. troposphere B. stratosphere C. mesosphere and ionosphere D. thermosphere

Answers and Explanations

  1. The correct answer is A.

    Most humans live close to the Earth’s surface, so they live in the layer that has the smallest altitude (the troposphere), making Choice (A) correct.

  2. The correct answer is C.

    From the table, you can see that the temperature of the mesosphere and ionosphere can be as low as –212 degrees, which is colder that any of the other layers, making Choice (C) the correct answer.

About This Article

This article is from the book:

About the book author:

Stuart Donnelly, PhD, earned his doctorate in mathe-matics from Oxford University at the age of 25. Since then, he has established successful tutoring services in both Hong Kong and the United States and is considered by leading educators to be one of the most experienced and qualified private tutors in the country.

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