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

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

Answer: (C)

Verified step by step guidance

1. Understand that the question is about the composition of Earth's crust, which is the outermost solid layer of the Earth.
2. Recall that Earth's crust is primarily made up of certain elements that are more abundant than others due to geological processes and mineral formation.
3. Identify that oxygen is the most abundant element in the Earth's crust because it forms many compounds, especially oxides and silicates.
4. Recognize that silicon is the second most abundant element, as it combines with oxygen to form silicate minerals, which dominate the crust.
5. Conclude that the two most abundant elements in Earth's crust are oxygen and silicon, making them the correct answer.