Answer:
B) neutron-proton.
Step-by-step explanation:
By given, we know that "a force can exist between two charged particles or objects even if they're as small as subatomic particles".
Having said that, the pair of particles without a force is neutron-proton, basically because the neutron is not a charged particle.
According to physics, this two subatomic particles are held together by the forces exerted by quarks, which are smalles subatomic particles.
So, if you notice, the answer is deducted from the problem itself, because it mentioned about charged particles, and neutrons are not charged.
Therefore, the right answer is B.