Answer:
C
Step-by-step explanation:
Most discussions of refraction will have a diagram similar to that of C.
The angle of incidence is measured from the normal to the boundary, as is the angle of refraction. The product of the sine of the angle and the index of refraction is the same for the media on either side of the boundary.
n₁·sin(θ₁) = n₂·sin(θ₂)
For media, such as optical fiber, that has an index of refraction greater than 1, the angle of refraction will be smaller in that media than the angle of incidence coming from air.
Figure C applies.