The correct answer is: a) The Western Ghats.
The Western Ghats are a mountain range that runs along the western coast of India. They are a major source of rainfall for the region, and they are home to many rivers. The rivers that flow from the Western Ghats are used to generate hydroelectric power.
The Eastern Ghats are a mountain range that runs along the eastern coast of India. They are not as high as the Western Ghats, and they do not receive as much rainfall. As a result, they are not as well-suited for hydroelectric power generation.
The coastal plains are located along the coast of India. They are relatively flat, and they are not well-suited for hydroelectric power generation.
River deltas are formed where rivers meet the ocean. They are low-lying areas, and they are not well-suited for hydroelectric power generation.
In conclusion, the Western Ghats are the best place to generate hydroelectric power in Tamil Nadu.