Explanation:

Sangam texts prominently mention only the ports of Musiri, Puhar (Kaveripattinam) and Korkai, the three great ports of the three great rulers of the times. However, the Periplus refers to the ports of Tondi, Musiri and Comari (Cape Comorin / Kanyakumari), Colchi (Korkai), Poduke (Arikamedu) and Sopatma.
According to Periplus there were three types of vessels in use in South India. These included small coasting vessels, large coasting vessels and ocean-going ships. There is also the mention of large vessels called Colandia sailing from the Tamil Coast to the Ganges.

The Sangam texts most prominently mention the port of Puhar (Kaveripattinam).

So, the correct answer is 2. Puhar (Kaveripattinam).