Most people would be (1) by the high quality of medicine (2) to most Americans. There is a lot of specialization, a great deal of (3) to the individual, a (4) amount of advanced technical equipment, and (5) effort not to make mistakes because of the financial risk which doctors and hospitals must (6) in the courts if they (7) things badly.
But the Americans are in a mess. The problem is the way in (8) health care is organized and (9) . (10) to pubic belief it is not just a free competition system. The private system has been joined a large public system, because private care was simply not (11) the less fortunate and the elderly.
But even with this huge public part of the system, (12) this year will eat up 84.5 billion dollars—more than 10 percent of the U. S. Budget—large number of Americans are left (13) . These include about half the 11 million unemployed and those who fail to meet the strict limits (14) income fixed by a government trying to make savings where it can.
The basic problem, however, is that there is no central control (15) the health system. There is no (16) to what doctors and hospitals charge for their services, other than what the public is able to pay. The number of doctors has shot up and prices have climbed. When faced with toothache, a sick child, or a heart attack, all the unfortunate persons concerned can do is (17) up. Two thirds of the population (18) covered by medical insurance. Doctors charge as much as they want (19) that the insurance company will pay the bill.
The rising cost of medicine in the U. S. A. is among the most worrying problems facing the country. In 1981 the country’s health bill climbed 15.9 percent--about twice as fast as prices (20) general.
19（）
A. knowing
B. to know
C. they know
D. known
，虚线下方匀强磁场范围足够大，磁感应强度为
，现有质量为
、电量为
的带正电粒子从距电磁场边界
处无初速释放（带电粒子重力可忽略不计）．求： 
