a substance's density is the same at a certain pressure and temperature, and the density of one substance is usually different than another substance.
C.
remember
reactants ----> products
The question is poor. Light doesn't refract on its way THROUGH anything. It refracts at the boundary BETWEEN two different media. The effect is greatest where the ratio of the speeds of light in the two media is greatest. On your list, that would be at the boundary between air or space and glass.
