With reference to the period of Gupta dynasty in ancient India, the towns Ghantasala, Kadura and Chaul were well known as

Explanation

Both the coasts of India have been studded with a string of ports since the ancient time and involved in foreign trade. During the Gupta era, the ports of the east coast, Tamralipti, Ghantashala, and Kadura handled the north-Indian trade with south-east Asia, and those of the west coast, Broach, Chaul, Kalyan and Cambray, traded with the Mediterranean and west Asia but the more southerly of these ports were outside Gupta control. Therefore, the correct answer is (a).