Answer:
B. Electromagnetic force
Step-by-step explanation:
Electromagnetic force is the unification of two forces
1) Electrostatic force
2) Magnetic force
here we know that electrostatic force is the force of attraction or repulsion due to two static charges placed near to each other
Magnetic force is the force between two magnetic material or two moving charges which produce magnetic field near each other
So unification of two fundamental forces is used in case of electromagnetic force.