For an increasing number of students at American universities, Old is suddenly in．The reason is obvious: the graying of America means jobs．Coupled with the aging of the baby-boom(生育高峰)generation, a longer life span means that the nation's elderly population will expand greatly over the next 50 years．By 2050,25 percent of all Americans will be older than 65,up from 14 percent in 1995．The change sets questions for government and society, of course．But it also creates career opportunities in medicine and health professions, and in law and business as well．“In addition to the doctors, we're going to need more sociologists, biologists, urban planners and specialized lawyers,” says Professor Edward Schneider of the University of Southern California's (USC) School of Gerontology(老年学)．
Lawyers can specialize in“elder law”, which covers everything from trusts and estates to nursing-home abuse(虐待) and age discrimination(歧视)．Businessmen see huge opportunities in the elder market because the baby boomers,74 million strong, are likely to be the wealthiest group of retirees in human history．“Any students who combines an expert knowledge in gerontology with, say, an MBA or law degree will have a license to print money, ”one professor says．
Margarite Santos is a 21-year-old senior at USC．She began college as a biology major but found she was “really bored with bacteria．” So she took a class in gerontology and discovered that she liked it．She says,“I did volunteer work in retirement homes and it was very satisfying．”
小题1:“．．．Old is suddenly in”(Line 1, Para．1) most probably means “_______”．
A．America has suddenly become a nation of old people
B．gerontology has suddenly become popular
C．more elderly professors are found on American campuses
D．American colleges have been full of old students小题2:Why can businessmen make money in the growing elder market?
A．Retirees are more willing to spend money．
B．They can employ more gerontologists．
C．The elderly have a great purchasing power(购买力)．
D．There are more elderly people working than before．小题3:Who can make big money m the new century according to the passage?
A．Retirees who are willing to spend money．
B．The volunteer workers in retirement homes．
C．College graduates with an MBA or law degree．
D．Professionals(专业人员)with a good knowledge of gerontology．小题4:It can be seen from the passage that the increase of America's elderly population_______．
A．will provide good job opportunities in many areas
B．will be just an unbearable burden on society
C．may lead to nursing home abuse and age discrimination
D．will create more students in universities
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时，小球b在轨道最高点对轨道无压力
，才能使两球在管内做圆周运动
，小球a对轨道最低点的压力比小球b对轨道最高点的压力大6mg