Which of the following statements is/are correct ?

I. In LCR series ac circuit, as the frequency of the source increases, the impedance of the circuit first decreases and then increases.
II. If the net reactance of an LCR series ac circuit is same as its resistance, then the current lags behind the voltage by 45°.
III. Below resonance, voltage leads the current while above it, current leads the voltage.

 I and II

1. In LCR series ac circuit, as the frequency of the source increases, the impedance of the circuit first decreases and then increases.
2. If the net reactance of an LCR series ac circuit is same as its resistance, then the current lags behind the voltage by 45°.