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  3. In the early 1960s Wilt Chamberlain was one of only three players in the National Basketball Association (NBA) listed at over se

In the early 1960s Wilt Chamberlain was one of only three players in the National Basketball Association (NBA) listed at over se

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问题    In the early 1960s Wilt Chamberlain was one of only three players in the National Basketball Association (NBA) listed at over seven feet. If he had played last season, however, he would have been one of 42. The bodies playing major professional sports have changed dramatically over the years, and managers have been more than willing to adjust team uniforms to fit the growing numbers of bigger, longer frames.
   The trend in sports, though, may be obscuring an unrecognized reality: Americans have generally stopped growing. Though typically about two inches taller now than 140 years ago, today’s people especially those born to families who have lived in the U. S. for many generations-apparently reached their limit in the early 1960s. And they aren’t likely to get any taller. "In the general population today, at this genetic, environmental level, we’ve pretty much gone as far as we can go, " says anthropologist William Cameron Chumlea of Wright State University. In the case of NBA players, their increase in height appears to result from the increasingly common practice of recruiting players from all over the world.
   Growth, which rarely continues beyond the age of 20, demands calories and nutrients-notably, protein-to feed expanding tissues. At the start of the 20th century, under-nutrition and childhood infections got in the way. But as diet and health improved, children and adolescents have, on average, increased in height by about an inch and a half every 20 years, a pattern known as the secular trend in height. Yet according to the Centers for Disease Control and Prevention, average height-5’9" for men, 5’4" for women-hasn’t really changed since 1960.
   Genetically speaking, there are advantages to avoiding substantial height. During childbirth, larger babies have more difficulty passing through the birth canal. Moreover, even though humans have been upright for millions of years, our feet and back continue to struggle with bipedal posture and cannot easily withstand repeated strain imposed by oversize limbs. "There are some real constraints that are set by the genetic architecture of the individual organism, " says anthropologist William Leonard of Northwestern University.
   Genetic maximums can change, but don’t expect this to happen soon. Claire C. Gordon, senior anthropologist at the Army Research Center in Natick, Mass. , ensures that 90 percent of the uniforms and workstations fit recruits without alteration. She says that, unlike those for basketball, the length of military uniforms has not changed for some time. And if you need to predict human height in the near future to design a piece of equipment, Gordon says that by and large, "you could use today’s data and feel fairly confident. "
The text intends to tell us that______.
选项 A、the change of human height follows a cyclic pattern
B、human height is becoming even more predictable
C、Americans have reached their genetic growth limit
D、the genetic pattern of Americans has altered
答案C
解析 选项A的意思是：人类的身高改变遵循着周期的模式。文章中没提到这点。选项B的意思是：人类的身高变得更加具有可预知性。文中表达美国人增长的尺度到达了极限，没有提到整个人类的身高的尺度问题。选项D的意思是：美国人的基因形态已改变，文中未提到这个内容。选项C的意思是：美国的身高人已经达到了基因增长的极限。文中就要说明由于基因的限制，美国人已经达到了身高的极限。所以下面要谈的问题还是与此相关的具体论证。故答案为C。
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