Which of the following is NOT listed as part of the water cycle?

• A. Osmosis
• B. Transpiration
• C. Runoff
• D. Groundwater (aquifer)

Answer: (A)

The water cycle describes how water moves through Earth’s systems—evaporation from oceans and plants, condensation into clouds, precipitation, and then processes that move water across the land such as infiltration, runoff, and groundwater flow, with transpiration returning water vapor from plants to the atmosphere. Osmosis is a cellular process where water moves across a membrane to balance solute concentrations inside and outside cells. It happens inside organisms and isn’t considered a stage of the Earth's water cycle. The other options—transpiration, runoff, and groundwater—are all part of how water circulates on our planet, so they fit the cycle.