At What Angle with the Normal to the Surface of the Water

At what angle with the normal to the surface of the water must a beam of light enter the water so that the refracted beam makes an angle of 10 ^$\circ$ to the normal of the water?

A) 10 ^$\circ$
B) 13 ^$\circ$
C) 15 ^$\circ$
D) 17 ^$\circ$
E) 20 ^$\circ$