Question

clouds are formed when
sunlight causes water droplets to evaporate.
liquid water condenses on grass and windows.
raindrops freeze into tiny pellets and fall to earth.
water vapor in the air condenses to form liquid water or ice.

Explanation:

Cloud formation occurs when water vapor in the air cools and condenses. Evaporation (sunlight causing water droplets to evaporate) is the opposite of cloud - forming. Liquid water condensing on grass and windows is dew, not cloud formation. Raindrops freezing into tiny pellets and falling to Earth is sleet, not cloud formation. Clouds form when water vapor in the air condenses to form liquid water or ice.

Answer:

water vapor in the air condenses to form liquid water or ice.