Transmissibility is unity at two points.
Which one of the following is true for these two points?
(a) $\omega /\omega _{n}$ is zero and $\sqrt{3}$for all values of damping
(b) 
$\omega /\omega _{n}$ is zero and $\sqrt{2}$ 
for all values of damping
(c) $\omega /\omega _{n}$ is unity and 2 for all values of damping
(d)$\omega /\omega _{n}$ is unity and $\sqrt{3}$ for all values of damping