Answer
Sphere A and sphere C repel each other.
Sphere B and sphere D repel each other.
All other pairs of spheres attract each other.
Work Step by Step
Sphere A and sphere C are both positively charged, so they repel each other since like charges repel. Sphere B and sphere D are both negatively charged, so they repel each other since like charges repel.
A positively charged sphere and a negatively charged sphere attract each other since opposite charges attract each other.
When a positively charged sphere is brought near a neutral sphere, the electrons in the neutral sphere are attracted to the positive charges so a positively charged sphere and a neutral sphere attract each other.
When a negatively charged sphere is brought near a neutral sphere, the electrons in the neutral sphere are pushed away toward the opposite side of the neutral sphere. This exposes positive charges in the neutral sphere which are attracted to the negatively charged sphere. Therefore, a negatively charged sphere and a neutral sphere attract each other.
