With reference to ancient South India, Korkai, Poompuhar and Muchiri w

With reference to ancient South India, Korkai, Poompuhar and Muchiri were well known as

capital cities
ports
centres of iron-and-steel making
shrines of Jain Tirthankaras
This question was previously asked in
UPSC IAS – 2023
Option B is correct.
Korkai, Poompuhar, and Muchiri were famous port cities in ancient South India, particularly important during the Sangam age for maritime trade with foreign entities, including the Roman Empire.
Korkai was a major port city of the Pandyas on the east coast, known for its pearl fishery. Poompuhar (also known as Kaveripattinam) was the principal port of the Cholas, located at the mouth of the Kaveri river on the east coast, and was a bustling center of trade. Muchiri (or Muziris) was a significant port on the west coast, controlled by the Cheras, playing a crucial role in trade with the Roman world, exchanging spices, pearls, gems, etc., for gold and other goods. While these cities might have had other aspects (like nearby capitals or craft centers), they were primarily renowned as major ports facilitating extensive trade networks.