What is the main difference between a proton and a neutron? Select one:
a. Size is the main difference
b. Charge is the main difference
c. Location in the atom in the main difference
d. Radioactivity is the main difference

b. Charge is the main difference

Explanation:

This is a theory question which you just need to understand and remember the concepts.

Protons and neutrons are relatively the same sizes.

The charges here are defined, protons are positively charged and neutrons have no charge (electrically neutral).

Both are located in the nucleus of an atom.

Proton radiation rarely occurs and neutron radiation is a form of ionizing radiation in cases typically of nuclear fission or nuclear fusion.

The most likely answer is that the charge is the main difference. This is also a basic concept so this would be the answer.