Between noon and 2 pm, the amount of water in the rain gauge decreased.
This can be caused by evaporation, which turns water into water vapor.
Precipitation would increase the amount of rain water in the gauges, not decrease it.
Condensation occurs after evaporation but wouldn't decrease the water in the gauges by itself.
Runoff is when water on land drains into water sources such as lakes, rivers, oceans, etc.
So the answer is A. evaporation.