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

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.

A．schooling and training
B．facilities he or she uses.
C．practice in a hospital
D．education he or she provides