The portion of a light ray that falls on a surface is a/an
a. reflected ray.
b. diffuse reflection.
c. specular reflection.
d. incident ray.

So we want to know what is a light ray that falls on a surface. The incident ray that fallls on a surface can then fe reflected, refracted or transmitted. The angle in which the incident ray is must be the same as the angle of a refracted light ray. So the correct answer is D.