Answer
Choice E.
Work Step by Step
When light travels from a fast medium (low index of refraction n) to a medium where it slows down (relatively higher index of refraction), it bends toward the normal. The opposite happens when it travels from a high-n slow material to a lower-index fast material: it bends away from the normal.
The light ray passes from material 1 to material 2 and bends toward the normal.
This means that $n_{1} \lt n_{2}$.
The light ray then goes from 2 to 3, and bends away from the normal. This means that $n_{3} \lt n_{2}$.
We notice that it bends away from the normal very far, more than it would for the ray to end up parallel to the original ray in medium 1.
This means that $n_{3} \lt n_{1}$; Light travels faster in 3 than in 1. If light traveled faster in 1 than in 3, the ray would not have bent away from the normal quite so much.
Combining these three relations indicates choice E.
