Question: 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: 
 A. They can be solids, liquids, or gases.
 B. They come in different sizes and shapes.
 C. They combine in different numbers and ratios.
 D. They can be a proton, a neutron, or an electron. 
Answer: C