Aray of yellow light ( f8= 5.09 × 1014 hz) travels at a speed of 2.04×10 meters per second in

The complete question in the attached figure
Let
c ------------------- > is the speed of light
v ------------------- > is the speed in medium
n ------------------- > is the refractive index of medium
we know that
c/v = n
n = (3 x 10^8)/(2.04 x 10^8) = 1.47

1.47 is the refractive index of glycerol.
therefore

the answer is (4) glycerol

The correct choice is c