The refractive index of medium A is least that is 1.31, so the velocity of lght will be maximum in medium A.
We know that the relationship between velocity and refractive index is given by:
n= refractive index of medium
c= Velocity of light in vaccum
v= Velocity of light in that medium
Rearranging the above equation we get
v=c / n
Velocity and refractive index are inversly porportional.
Hence when the refractive index is smaller the velocity of light will be maximum.
So the medium A having the least refractive index will have the maximum velocity.