Question

if a material has a high index of refraction, it has a
low optical density, and light travels more quickly through it.
high optical density, and light travels more quickly through it.
high optical density, and light travels more slowly through it.
low optical density, and light travels more slowly through it.

Explanation:

The refractive index of a material is directly related to its optical density: a higher refractive index means higher optical density. Additionally, the speed of light in a material $v$ is given by $v=\frac{c}{n}$, where $c$ is the speed of light in a vacuum and $n$ is the refractive index. A larger $n$ (higher refractive index) results in a slower speed of light in the material.

Answer:

high optical density, and light travels more slowly through it.