Electromagnetic force is present when electromagnetic fields
a- become charged as they lose electrons.
b- become stable as they come in contact with other forces.
c- interact with charged particles.
d- gain energy from other forces.

c- interact with charged particles.

Explanation:

When a charged particle is placed in the field of the other charged particle then it will experience electromagnetic force on it.

As we know that force on a charged particle due to some other electric field is given by

F = qE

here we know

q = charge

E = electric field intensity

Similarly when a charged particle is placed in external magnetic field then the force on that moving charge is given by

so here if charge is moving in the magnetic field due to some other system then the force on it is given by above equation.

So here we can say that electromagnetic force is present when electromagnetic fields

c- interact with charged particles.