Answer: The answer should be A: Precipitation.
Explanation: When we take a look at this question, it mentions that there is dew, fog, and clouds on the planet. Infiltration would have probably been evaporated from the ground and became a cloud. The dew and fog would be the condensation. The astronomers notice that there is never any rainfall, and precipitation in the water cycle is rainfall. So therefore, the missing part of the water cycle would be precipitation
