Normal reaction:
Arises due to contact between bodies.
At the bottom, it is due to electromagnetic interaction.
Force of Friction:
Arises due to contact between bodies.
Force between two neutrons:
It is due to nuclear force
It is a force due to the strong nuclear force field
Force between two protons:
It is due to nuclear force
It is a force due to the strong nuclear force field
Coulomb repulsion between two protons id electromagnetic force