Consider the situation shown in following fig. The capacitor A has a charge q on it whereas B is uncharged. The charge appearing on the capacitor B, a long time after the switch S is closed is
zero
Since the outer plate of B is free, there cannot be any charge accumulation on it and the magnitude of the charge on the plates of a parallel plate capacitor is equal. So, there cannot be any charge on the capacitor B. Hence the correct choice is (a).