He could make a macromolecule which is made up of carbon and hydrogen only.
Explanation:
An atom a fundamental piece of matter that constitutes a chemical element.
A molecule is a group of atoms bonded together. It represents the smallest fundamental unit of a chemical compound that can participate in a chemical reaction.
The red balls denote the hydrogen and black balls denote the carbon. He could make a macromolecule which is made up of carbon and hydrogen only.
