The Three Factors That Determine the Interference of Reflected Waves

The three factors that determine the interference of reflected waves from a thin film are:

A) incoming wavelength, speed of light in vacuum, thickness of the film
B) shifts in wavelength on reflection, path length difference, index of refraction of the film
C) incoming wavelength, index of refraction of the external medium, index of refraction of the film
D) shifts in wavelength on reflection, index of refraction of the film, speed of light in vacuum
E) path length difference, thickness of the film, index of refraction of the film