Why Does the Sun Look Red When It Is Setting

Multiple Choice

Why does the Sun look red when it is setting?

A) Red is the Sun's natural color as determined by Wien's law, but it is only when the Sun is close to the horizon that sunlight can pass through the atmosphere unfiltered.
B) When the Sun is close to the horizon, it is traveling away from the observer at great speed, and the Doppler shift makes it look red.
C) Earth's atmosphere scatters longer wavelength light more easily than shorter, so more red light is scattered out of the sunlight and into observers' eyes.
D) Earth's atmosphere scatters shorter wavelength light more easily than longer, so more red light is left to reach observers' eyes.