Index.of Photobucket Help With A Physics Question Please?

Help with a physics question please? - index.of photobucket

The diagram shows the passage of a light beam
Air into a substance X. The refractive index
X (Nair = 1)
0.74
B 1.15
1.29 C
D 1.35
1.47E

Image is shown here http://i59.photobucket.com/albums/g311/x ...