Light Enters the Smooth Flat Surface of a Block of Glass

Multiple Choice

Light enters the smooth flat surface of a block of glass from the vacuum of space (e.g., a spacecraft window) . What is the speed of light inside the glass compared to that in a vacuum?

A) The speed will depend on the angle that the light ray makes with the perpendicular to the surface, becoming slower as the angle increases.
B) same because the speed of light is constant, by definition
C) faster because the glass is denser than the vacuum
D) slower because the glass is denser than the vacuum