The whiteness of clouds is mainly due to scattering, which occurs when sunlight is scattered in all directions by tiny water droplets or ice crystals. This scattering causes all colors of light to be evenly distributed, making clouds appear white. Therefore, the correct answer is C. scattering.
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The whiteness of clouds is mainly due to scattering, where sunlight is scattered in all directions by tiny water droplets or ice crystals. This scattering results in the equal distribution of all colors of light, making clouds appear white. Reflection and polarization are less significant in determining cloud color. ;