According to the passage, how long does it take for a would-be physician to become an independent physician in the USA

A．they may have more patients
B．they can take turns to work long hours
C．facilities may be a big burden to an individual
D．no one wants to assume too much responsibility

A．Physicians' expensive education and the characteristics of their work make them well deserve the handsome pay.
B．It is reasonable for physicians to have a large income because their work is very dangerous.
C．Physicians should be better paid because they work long hours under bad conditions.
D．Physicians shoulder great responsibilities, so it is understandable that they should be well rewarded.