A Ray of Light Enters an Equilateral Prism Made of Material

Multiple Choice

A ray of light enters an equilateral prism made of material with n = 1.45.What angle of incidence, $\theta$ ,will cause the internally refracted ray to be parallel to the base of the prism?

A) 46.5 $^{\circ}$
B) 30.0 $^{\circ}$
C) 20.2 $^{\circ}$
D) 5.70 $^{\circ}$
E) this cannot happen