Answer:
B. "Matter exists only when you can see it."
Explanation:
Since an atom is the smallest unit of matter, both "atoms make up matter" and "matter is made up of atoms" are true.
Living things like lions or plants are made up of atoms, which is the smallest unit of matter.
This means that by the process of elimination, B. is correct.
Matter exists regardless if you can see it or not. Humans cannot see air, but it is still made up of oxygen atoms (which are matter).
