The major base of the Indian Navy at Karwar is called INS Kadamba. The Indian Navy operates various naval bases across the country, and INS Kadamba is one of them. It is located in Karwar, which is a city in the Uttara Kannada district of Karnataka, India.

Option 2, INS Vikramaditya, is incorrect. INS Vikramaditya is actually a aircraft carrier of the Indian Navy, and it is based in the Indian state of Goa.

Option 3, INS Harshvardhan, is also incorrect. There is no base with this name in Karwar or anywhere else in India.

Option 4, INS Kushan, is incorrect as well. There is no base named INS Kushan in Karwar or any of the Indian Navy bases.

In conclusion, the correct answer to the question is option 1, INS Kadamba, which is the name of the major base of the Indian Navy at Karwar.