Answer:
C.An electric field exists between the glass rod and the pith ball, causing the attraction.
Explanation:
A object has a charge when they have excess or deficient number of electrons in order to have a neutral charge. The object has a negative charge when it has more electrons while it is positive when it has less electrons to remain neutral. Any charged object has an electrical field around it. Attraction only takes place when one object has excess electrons and the other object is electron deficient. They attract each other in order to become neutral. This is the case that is seen here.
So, the attraction is caused due to an electric field exists between the glass rod and the pith ball, causing the attraction.