The main kharif cropping season in Tamil Nadu coincides with the southwest monsoon. The southwest monsoon is a seasonal wind that blows from the southwest towards the northeast across the Indian subcontinent during the summer months. It is the main source of rainfall for India, and it is responsible for the cultivation of many crops, including rice, sugarcane, and cotton.
The northeast monsoon is a seasonal wind that blows from the northeast towards the southwest across the Indian subcontinent during the winter months. It is a much weaker wind than the southwest monsoon, and it does not provide as much rainfall.
The summer season in Tamil Nadu is hot and dry, and it is not suitable for the cultivation of most crops.
The winter season in Tamil Nadu is cool and dry, and it is also not suitable for the cultivation of most crops.
Therefore, the correct answer to the question is “Southwest monsoon”.