The correct answer is: a) Ordinary.
Ordinary buses are the most common type of bus offered by GSRTC. They are designed for short-distance travel within cities and towns. They are usually not air-conditioned and have a basic level of amenities.
AC Sleeper buses are designed for long-distance travel. They have comfortable seats that recline and can be converted into beds. They also have air conditioning, toilets, and entertainment systems.
Volvo Multi-axle buses are the most luxurious type of bus offered by GSRTC. They are designed for long-distance travel and have all the amenities of an AC Sleeper bus, plus additional features such as power outlets and USB ports.
Rajdhani Express is a train service operated by Indian Railways. It is one of the fastest trains in India and offers a high level of comfort and amenities. It is not a bus service.