Because it is the farthest away from the light source. Although C is the intended answer, A is an unintended consequence. As light passes fromone medium to another, its speed changes. The frequency of the light does not change, so the wavelength has to. Reflection is the return of light rays from a surface.
Refraction is the bending of a ray of light.
All of the above. As far behind the mirror as the object is in front of the mirror. Half the distance of the object in front of the mirror. A Quarter of the distance of the object in front of the mirror. When light incidence on a rough surface is reflected in many directions.