Correct Answer is Option (A)

The resonance wave becomes very sharp when damping force is small.

Correct Answer is Option (D)

This is a case of damped vibration as the amplitude of vibration is decreasing with time.
Amplitude of vibrations at any instant t is given by $a=a_0{e}^{–bt}$, where $a_0$ is the initial amplitude of vibrations and b is the damping constant.

Now, when t = 100T, $a=a_0/3$  [T is time period]

Let the amplitude be $a^{\prime }$ at t = 200T.
i.e. after completing 200 oscillations.

$\therefore$ $a=a_0/3=a0e^{–100Tb}$   ...(i)

and $a^{\prime }=a_0{e}^{–200Tb}$ ...(ii)

From (i), $\frac{1}{3}=e^{-100Tb}$
$\therefore$ $e^{-200Tb}=1/9$

From (ii), $a^{\prime }=a_0\times \frac{1}{9}=\frac{a_0}{9}$

$\therefore$ The amplitude will be reduced to 1/9 of initial value.