Which of the following elements is the most abundant in the Earth's crust?

• A. Oxygen (O)
• B. Aluminum (Al)
• C. Silicon (Si)
• D. Iron (Fe)

Answer: (A)

Verified step by step guidance

1. Understand that the Earth's crust is composed of various elements, but some are more abundant than others based on geological studies and chemical analysis.
2. Recall that oxygen is a major component of many minerals in the crust, often combined with silicon and other elements to form silicate minerals.
3. Recognize that silicon is the second most abundant element in the crust, primarily found in silicate minerals, but it is less abundant than oxygen.
4. Note that aluminum and iron are also common elements in the crust but occur in smaller proportions compared to oxygen and silicon.
5. Conclude that oxygen is the most abundant element in the Earth's crust because it forms the majority of the compounds that make up the crust's minerals.