Which of the ray diagram is correct?

The correct option is C

Given, refractive index of medium A $\left({\mu }_A\right)$ = 3 and refractive index of medium B $\left({\mu }_B\right)$ = 4.
Since, $\left({\mu }_A\right)$ = 3 < $\left({\mu }_B\right)$ = 4
So, medium A is a rarer medium then medium B.

Also, light is travelling from medium A to medium B

We know that when a ray of light is travelling from a rarer to a denser medium then it bends towards the normal.