Final answer:
Electromagnetic force affects subatomic particles with charge, specifically electrons and protons, thus the correct answer is d. Both A and B.
Step-by-step explanation:
The electromagnetic force affects subatomic particles that have charge. In an atom, electrons, which have a negative charge, and protons, which have a positive charge, are influenced by electromagnetic forces such as the Coulomb force. Therefore, the correct answer to which subatomic particles are affected by electromagnetic force is d. Both A and B, meaning both electrons and protons. Neutrons, on the other hand, do not have a charge and are not directly affected by electromagnetic forces; they are held in the nucleus due to the strong nuclear force.