Which two elements are the most abundant in Earth's crust?

• A. Hydrogen and carbon
• B. Iron and aluminum
• C. Oxygen and silicon
• D. Calcium and sodium

Answer: (C)

Verified step by step guidance

1. Understand that the Earth's crust is composed of various elements, but some are much more abundant than others.
2. Recall that oxygen is the most abundant element in the Earth's crust, making up a significant portion of its composition.
3. Recognize that silicon is the second most abundant element, commonly found combined with oxygen in minerals like silicates.
4. Compare the given options and identify that 'Oxygen and silicon' are the two elements that dominate the Earth's crust.
5. Note that other elements like iron, aluminum, calcium, sodium, hydrogen, and carbon are present but in smaller amounts compared to oxygen and silicon.