Question

clouds appear to be white because typical cloud droplets (about 10 μm in diameter):
a. selectively scatter violet and blue wavelengths.
b. scatter all wavelengths of visible light equally.
c. absorb violet and blue wavelengths.
d. selectively scatter yellow, green, and red wavelengths.

Explanation:

White light is a combination of all visible - light wavelengths. Cloud droplets scatter all wavelengths of visible light equally, which makes clouds appear white. When all visible - light wavelengths are scattered in equal amounts, our eyes perceive the combination as white.

Answer:

B. scatter all wavelengths of visible light equally.