Natural Science CLEP Prep Practice Exam

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Prepare for the CLEP Natural Science Exam with our comprehensive study materials and practice questions. Test your knowledge and ace the exam by mastering key concepts.

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What is the most abundant element in the Earth’s crust?

Oxygen
Iron
Carbon
Hydrogen

The correct answer is: Oxygen

Oxygen is the most abundant element in the Earth’s crust, making up about 46.6% of its mass. This is because oxygen is a major component of the most common minerals found in the crust, such as silica and feldspar. Iron is the second most abundant element, making up about 27.7% of the crust's mass. While this is still a significant amount, it is much less than oxygen. Carbon is present in the Earth's crust, but in much lower amounts, typically less than 0.2% of the crust's mass. It is mainly found in carbonate minerals and organic matter. Hydrogen is not considered to be a major component of the Earth's crust, as it is a gas at normal crustal temperatures and does not form stable minerals.