The Portuguese were the first Europeans to establish a trading post in Tamil Nadu at:

The correct answer is: b) Nagapattinam.

The Portuguese were the first Europeans to establish a trading post in Tamil Nadu at Nagapattinam in 1507. The Portuguese were interested in establishing trade with India because they wanted to obtain spices, such as pepper, cloves, and nutmeg, which were in high demand in Europe. Nagapattinam was a good location for a trading post because it was a port city that was located on the Coromandel Coast, which was a major trade route between India and Southeast Asia. The Portuguese built a fort at Nagapattinam and used it to control the trade in the region. They also converted many of the local people to Christianity.

The other options are incorrect because:

• Chennai was founded by the British in 1639.
• Puducherry was founded by the French in 1674.
• Thoothukudi (Tuticorin) was a major port city during the Chola dynasty, but it was not a major trading post for the Portuguese.