Answer:
D It must be equal to 1.00
Explanation:
The refraction in the second medium must be equal to 1. The refraction index is given as the ration of the angle of incidence to the angle of refraction. This is given as a fraction. In other words:

where Θ₁ and Θ₂ are angles of incidence an refraction, and n is the refractive index.
At a critical angle, the refraction is equal to the reflection inside the medium. This results in a phenomenon called total internal reflection where light is reflected internally in the medium.
If you increase the frequency, the photon will have more energy and can therefore transfer more electrons to the other side. As such, you will have an increased current.
If you use up renewable resources faster than you can reproduce them, then they're really non-renewable. For example, if you're cutting down trees faster than they're growing, then you'll eventually run out of trees, even though they're "renewable". Technically, oil is renewable, but it takes millions of years to create, so it's non-renewable.