Answer:
groundwater
Step-by-step explanation:
Precipitation is any type of water that forms in the Earth's atmosphere and then drops onto the surface of the Earth. Water vapor, droplets of water suspended in the air, builds up in the Earth's atmosphere before precipitating.
Unlike the other three options (balls of hail, sleet, and snowflakes), groundwater is the only option that is not directly a form of precipitation.
Hail is a form of precipitation as hailstones are formed by layers of water attaching and freezing in a large cloud.
Sleet is a form of precipitation as it is formed when a snowflake partially melts but then refreezes.
Snowflakes are a form of precipitation that falls in the form of ice crystals.