Power delivered by the $ac$ source of the circuit becomes maximum when

Match List-$I$ with List-$II$ :

List-$I$	List-$II$
$(a)$ $\omega L > \frac{1}{\omega C}$	$(i)$ Current is in phase with $emf$
$(b)$ $\omega L = \frac{1}{\omega C}$	$(ii)$ Current lags behind the applied $emf$
$(c)$ $\omega L < \frac{1}{\omega C}$	$(iii)$ Maximum current occurs
$(d)$ Resonant frequency	$(iv)$ Current leads the $emf$

Choose the correct answer from the options given below :

In an $L-C-R$ series circuit,the value of only capacitance $C$ is varied. The resulting variation of resonance frequency $f_0$ as a function of $C$ can be represented as

$A$ series $LCR$ circuit containing a resistance $R$ has angular frequency $\omega$. At resonance,the voltage across the resistance and the inductor are $V_R$ and $V_L$ respectively. Then,the value of inductance $L$ will be:

The frequency at resonance for the circuit shown in the figure is:

What is the sharpness of resonance and obtain an equation for the $Q$ factor?