Materials can be categorized as being conductors or insulators. Conductors are those materials that allow the free flow of electrons from atom to atom across their surface. Insulators prevent the free flow of such electrons.  This property makes the behavior of conductors quite different than that of  insulators when they are touched to a charged object or to the ground.
 

Like all questions in Conductors and Insulators, you will need to ...

• Identify whether Object A (and B and C) is a conductor or an insulator.
• Identify whether Object A (or B or C) is being touched by neutral ground or by a charged object.

What's Happening?
When a charged conductor is touched to a neutral conductor, there is a flow of electrons between the two conductors, resulting in the neutral object acquiring a charge. The process is known as charging by conduction or charging by contact. The type of charge acquired by the neutral object is identical to the type of charge on the charged object. Only conductors can conduct their charge to other conductors in this manner. Insulators cannot be charged by conduction since such materials prevent the flow of electrons from atom to atom across their surface.