They don't have a science option but:

As light travels from air to water to glass, it will refract. The best explanation for this would be

A)
Glass is less transparent than water, which is less transparent than air.

B)
Light will be transmitted into the new medium each time it reaches a boundary.

C)
A light wave reflects off molecules as it travels, this causes the light to bend,

D)
The speed of a wave slows as it travels at different speed in different media.