The Speed of Light Generally Decreases When It Passes Through $\times$

The speed of light generally decreases when it passes through media other than a vacuum.The speed,v,is approximately c (2.998 $\times$ 10⁸m/s) divided by a quantity called the medium's refractive index, $\eta$ .In which of the following would the frequency of 193 nm light be the lowest? ( $v$ = c/ $\eta$ ; c = $\lambda$$v$ )

A) hydrogen, $\eta$ = 1.0001
B) carbon tetrachloride, $\eta$ = 1.461
C) silicone oil, $\eta$ = 1.520
D) water, $\eta$ = 1.3330
E) diamond, $\eta$ = 2.419