Answer:
d) electrons removed.
Step-by-step explanation:
Two insulators are electrically neutral, that is, the number of electrons and protons are equal. When one insulator is rubbed against another, electrons are removed from one of the insulators due their high mobility. The insulator which lost the electrons becomes positively charged while the one that gained the electron becomes negatively charged.
Therefore, when rubbing two insulators together, the one that gets a positive charge has had electrons removed.