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刷刷题刷刷变学霸
举一反三
【单选题】空中信道建立过程中，小区收到手机发来的SABM帧后，要发回一个内容一样的UA帧，目的是（）
A.
验证信道载干比是否符合GSM要求
B.
为了手机正确占用信道
C.
验证手机的信息是否正确到达基站
D.
以上都是
【单选题】49（） A. Talking on a cell phone while driving brings you joy anyway. B. The estimate is based on surveys with office workers. C. The younger group did 10 percent better when not interrupted. D. Howeve...
A.
A Bad Idea
B.
Think you can walk, drive, take phone, calls, e-mail and listen to music at the same time Well, New York’s new law says you can’t (46) The law went into force last month, following research and a shocking number of accidents that involved people using electronic gadgets(小巧机械)when crossing the street.
C.
Who’s to blame (47) "We are under the impression that our brain can do more than it often can," says Rene Marois, a neuroscientist(神经科学家)in Tennessee. "But a core limitation is the inability to concentrate on two things at once."
D.
The young people are often considered the great multitaskers. (48) A group of 18- to 21-year-olds and a group of 35-to 39-year-olds were given 90 seconds to translate images into numbers, using a simple code. (49) But when both groups were interrupted by a Phone call or an instant message, the older group matched the younger group in speed and accuracy.
E.
It is difficult to measure the productivity lost by multitaskers. But it is probably a lot. Jonathan Spira, chief analyst at Basex, a business-research firm, estimates the cost of interruptions to the American economy at nearly ＄ 650 billion a year. (50) The surveys conclude that 28 percent of the workers’ time was spent on interruptions and recovery time before they returned to their main tasks.