Natural Science CLEP Prep Practice Exam

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Prepare for the Natural Science CLEP Exam with our comprehensive quiz that includes multiple choice questions and detailed explanations. Boost your understanding and confidence to ace the test!

Each practice test/flash card set has 50 randomly selected questions from a bank of over 500. You'll get a new set of questions each time!

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Which gas makes up 78% of the Earth's atmosphere?

Nitrogen
Oxygen
Carbon dioxide
Methane

The correct answer is: Nitrogen

Nitrogen makes up 78% of Earth's atmosphere. Oxygen only accounts for 21%, while carbon dioxide and methane make up very small amounts. Carbon dioxide composes about 0.04% of the atmosphere, and methane makes up even less at around 0.00017%. Therefore, neither carbon dioxide nor methane are correct options for the gas that makes up 78% of Earth's atmosphere. It is important to note that while oxygen is a crucial gas for life on Earth, it does not make up the majority of the atmosphere as only a small portion is necessary for sustaining life.