The correct answer is: a) Bus services within Sikkim.
Sikkim Nationalized Transport (SNT) is a government-run department responsible for providing bus services within the Indian state of Sikkim. It was established in 1974 and has its headquarters in Gangtok. SNT operates a fleet of over 300 buses that connect all major towns and villages in Sikkim. The buses are well-maintained and comfortable, and offer a safe and reliable way to travel around the state.
Option b) is incorrect because private taxis are not regulated by SNT. Private taxis are operated by individual drivers and are not subject to the same rules and regulations as SNT buses.
Option c) is incorrect because air travel management is not a responsibility of SNT. Air travel in Sikkim is managed by the Airports Authority of India.
Option d) is incorrect because rail ticketing is not a responsibility of SNT. Rail ticketing is managed by the Indian Railways.