Question

What makes 50% of the Earth's crust?
A. Water
B. Carbon
C. Oxygen
D. Fossil
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Answer 1

Given the abundance of oxygen and silicon in the crust, it should not be surprising that the most abundant minerals in the earth's crust are the silicates.

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Abundances of the Elements in the Earth's Crust.

Element Approximate % by weight

Oxygen 50

Silicon 27.7

Aluminum 8.1

Iron 5.0

so oxygen is the answer