The correct answer is: b) Rainfall.
Many rivers in Tamil Nadu are seasonal, meaning that they flow only during certain times of the year. This is because the rivers are fed by rainfall, which is often seasonal in Tamil Nadu. During the monsoon season, which typically runs from June to September, there is heavy rainfall in Tamil Nadu. This rainfall causes the rivers to swell and flow. However, during the dry season, which typically runs from October to May, there is little rainfall in Tamil Nadu. This causes the rivers to dry up or flow very little.
The other options are incorrect because they are not the main source of water for rivers in Tamil Nadu. Snowmelt is not a major source of water in Tamil Nadu, as the state does not have any major mountain ranges. Groundwater is a source of water for rivers in Tamil Nadu, but it is not the main source. Dams and reservoirs can store water, but they do not create water.
In conclusion, the correct answer to the question “Many rivers in Tamil Nadu are seasonal, depending on: a) Snowmelt b) Rainfall c) Groundwater d) Dams and reservoirs” is b) Rainfall.