A student hangs a pith ball from a stand using thread and rubs a glass rod with silk cloth. Upon bringing the glass rod near the pith ball, the student observes that the pith ball is attracted towards the glass rod, as shown. How can the observation best be explained?
A. The glass rod exerts a gravitational force , causing it to attract the pith ball.
B. The pith ball exerts a replusion force towards the glass rod, causing the attraction
C. An electric field exists between the glass rod and the pith ball, causing the attraction
D. Electric charges in the string transfer to the pith ball, causing it to attract the glass rod.