When a glass rod is rubbed with a piece of silk cloth, the rod (a) and the cloth both acquire a positive charge. (b) becomes positively charged while the cloth has a negative charge. (c) and the cloth both acquire a negative charge. (d) becomes negatively charged while the cloth has a positive charge.

Soln:

The answer is (b) becomes positively charged while the cloth has a negative charge.

Explanation:

When two objects are rubbed against each other, they acquire opposite charges. By the law of convention, it is known that the rod acquires the positive charge, and the cloth acquires the negative charge.