Explanation:

- Option 1: Silicon

- Silicon is the second most abundant element in the Earth's crust. It makes up a significant portion of sand and rocks.

- Option 2: Aluminium

- Aluminium is the most abundant metal in the Earth's crust. It ranks third in overall abundance among the elements.

- Option 3: Carbon

- Carbon is essential for life and is found in all organic compounds, but it's not very abundant in the Earth's crust.

- Option 4: Oxygen

- Oxygen is the most abundant element on Earth, especially in the Earth's crust and atmosphere. It forms compounds with many other elements, like water and silica.