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.
The melting point of camphor is 178.4°C which is also the freezing point.
After the unknown substance is added, the freezing point is reduced to 173.6°C.
The freezing point depression is
178.4°C - 173.6°C = 4.8°C
The molar mass of the substance can be found using the equation
Kf m = 4.8
37.7 (0.664 / MW) = 4.8
MW = 5.22 g/mol
A. Heat is transferred from your hand to the ice cube.