Answer:
A. All the atoms in the substance are similar to each other.
Step-by-step explanation:
All the atoms in an element are similar to each other.
B. is probably wrong. Paul could be a brilliant student who can study substances on a scale that can be seen only under a microscope.
C. is wrong. All substances have energy.
D. is wrong. If there are many different types of atoms, the substance is a compound or a mixture.