Answer: The correct answer is the Normal.
Explanation:
When the incident ray enters the refracting surface, the ray bends from its original path because of the refractive index of the surface.
The angle of refraction is the angle which is made by the refracted ray and the perpendicular on the surface.
The perpendicular on the surface is known as Normal.
Hence, the angle of refraction is the angle between the refracted ray and the Normal.
