Sunsets are red because:
a) the cooler atmosphere in the evening absorbs more blue light.
b) sunlight must pass through more atmosphere then, and the atmosphere scatters even more light at bluer wavelengths, transmitting mostly red light.
c) sunlight must pass through more atmosphere then, and the atmosphere scatters more light at red wavelengths than bluer wavelengths.
d) the sun emits more red light when it's setting.
e) none of the above