The following words are all used to attract passengers EXCEPT ______.

A．service on the plane
B．a new safety device
C．flights within one country
D．charge-free air service

A．a successful airline in the 1980s meets the needs not only of the masses but also of the wealthy passengers
B．it is more comfortable to sit in the back of jet planes
C．business travelers dislike tourists
D．only by specializing in cheap flights can airlines avoid bankruptcy