Answer
Please see the work below.
Work Step by Step
(a) We know that at high frequency, the inductor behaves like an open circuit, while at low frequency, the same behavior is shown by the capacitor. Hence, we conclude that the current is the same in either case.
(b) We know that the best explanation is option (I) -- that is, the current is the same because at high frequency the inductor is like an open circuit and at low frequency the capacitor is like an open circuit. In either case the resistance of the circuit is R.
