The correct answer is: b) Siliguri.
Siliguri is a city in the Indian state of West Bengal. It is located in the foothills of the Himalayas, and is the gateway to the northeastern states of India. Siliguri is a major transportation hub, and is served by Bagdogra Airport, which is the nearest major airport to Sikkim.
Darjeeling is a town in the Indian state of West Bengal. It is located in the foothills of the Himalayas, and is a popular tourist destination. Darjeeling is not a major airport, and the nearest major airport to Darjeeling is Bagdogra Airport.
Guwahati is a city in the Indian state of Assam. It is the largest city in the northeastern states of India, and is a major transportation hub. Guwahati is not a major airport, and the nearest major airport to Guwahati is Bagdogra Airport.
Kolkata is a city in the Indian state of West Bengal. It is the capital of West Bengal, and the second most populous city in India. Kolkata is a major transportation hub, and is served by Netaji Subhas Chandra Bose International Airport, which is the nearest major airport to Kolkata.