They can be solids, liquids, or gases. They come in different sizes and shapes. They combine in different numbers and ratios. They can be a proton, a neutron, or an electron.
The elements carbon, hydrogen, and oxygen are parts of many different compounds. Which explains why these three elements can make so many different compounds?

Options:
- They can be solids, liquids, or gases.
- They come in different sizes and shapes.
- They combine in different numbers and ratios.
- They can be a proton, a neutron, or an electron.

They combine in different numbers and ratios.