Sunlight can be absorbed, , or scattered before it reaches Earth’s surface. About 30 percent of sunlight hits Earth directly, and 22 percent is filtered through . Dust particles short wavelengths, which causes the sky to appear blue. Earth radiates heat into the atmosphere, which traps the heat in gases, causing the .

The blank asks what sunlight is filtered through before reaching Earth’s surface. Clouds can absorb and scatter sunlight, so the sentence reads, “22 percent is filtered through clouds.” “Dust particles” are mentioned later as scattering short wavelengths, while gases trap heat in the atmosphere.

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