# A fish looking up through the water sees the outside world, contained in a circular horizon. If the refractive index of water is $\frac{4}{3}$ and the fish is 12 cm below the water surface, the radius of this circle in cm is :
( A ) $4 \sqrt{5}$
( B ) $36 \sqrt{7}$
( C ) $\frac{36}{\sqrt{7}}$
( D ) $36 \sqrt{5}$