The reason for the high medical cost mentioned in the article is that （）

A．they are not willing to pay high tuition for the doctors
B．they don't think it necessary to have medical care
C．they don't want to spend much money on it
D．they haven't got enough money to pay for it

A．a visit to a doctor's office may cost as much as $ 15 to $ 50 in U. S.
B．the cost of medical care is the main reason for the high costs in the U. S.
C．medical care in the U. S. costs a lot of money because doctors want to be rich
D．the high cost of tuition in medical schools is one reason for the high cost of medical care in the U. S.