What is the main difference between protons and neutrons

Ans C) protons have an electric charge but neutron have no charge

Explanation:

A protons have an electric charge but neutron have no charge.proton has positive charge of 1, that is, equal but opposite to the charge of an electron. A neutron, like the name implies, is neutral with no net charge. The charge is believed to be from the charge of the quarks that make up the nucleons (protons and neutrons).

grav force prop 1/r squared 2r all squared is 4rsquared 1/4rsquared quartered

that would be because of both gravity and friction. so     c