Officer Aptitude Rating (OAR) PracticeTest

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Study for the Officer Aptitude Rating Test with flashcards and multiple choice questions. Each question includes hints and explanations to help you understand your strengths and weaknesses. Prepare confidently for your exam!

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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What percentage of air is made up of oxygen?

21%
78%
0.04%
1%

The correct answer is: 21%

The composition of Earth's atmosphere is crucial for understanding various scientific and environmental concepts. Oxygen constitutes about 21% of the total volume of air. This percentage is significant because it supports life forms through the process of respiration. The remaining majority of the atmosphere is primarily made up of nitrogen, which accounts for approximately 78%. The other components, such as argon and carbon dioxide, comprise only trace amounts of the atmosphere. Carbon dioxide, for instance, is present at approximately 0.04%. This knowledge of the percentage of oxygen in the air is fundamental, particularly when considering its implications in fields like biology, environmental science, and atmospheric studies. Understanding that oxygen makes up 21% of the atmosphere helps explain its role in sustaining life and its interaction within various ecosystems.