The correct answer is: D. Total internal reflection.
Mirage is an optical phenomenon that occurs when light is refracted (bent) as it passes from one medium to another. In the case of a mirage, the light is refracted as it passes from the hot air near the ground to the cooler air above. This refraction causes the light to bend and appear to come from a different location than it actually is.
Total internal reflection occurs when light passes from a medium with a higher refractive index to a medium with a lower refractive index at an angle greater than the critical angle. The critical angle is the angle of incidence at which all of the light is reflected back into the first medium.
In the case of a mirage, the light is refracted as it passes from the hot air near the ground to the cooler air above. The hot air has a lower refractive index than the cooler air, so the light is refracted towards the ground. This refraction causes the light to bend and appear to come from a different location than it actually is.
The other options are not correct because they do not explain the phenomenon of mirage. Interference is the superposition of two or more waves that results in a new wave pattern. Diffraction is the bending of waves as they pass through a narrow opening or around an obstacle. Polarisation is the separation of light into waves that vibrate in a single plane.