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【简答题】
一次测试八年级若干名学生1分钟跳绳次数的频数分布直方图如图所示，请根据这个直方图回答下列问题： （1）已知自左至右第2、3组（组中值分别为145、155）的频率之和为0.28，第3、4、5组（组中值分别为155、165、175）的频率之和为0.8，则参加测试的总人数有______人，第3组的频数为______人，第4组的频率为______，并将直方图补充完整； （2）若图中自左至右各组的跳绳平均次数分别为137次，146次，156次，164次，177次，则参加测试的学生跳绳的平均次数为______（只需列出算式，不用计算结果）； （3）若测试所得数据的中位数是160次，则测试次数为160次的学生至少有______人．（直方图中每一组包括前一个边界值，不包括后一个边界值）
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【单选题】Although the dream of the home robot has not died, robots have had their greatest impact in factories. Unimate, the first industrial robot, went to work for General Motors in 1961. Even at a time when...
A.
the first robot of the world was designed in 1961 for General Motors
B.
the expensive computing power didn't hinder a robot's efficiency
C.
robots controlled by computers can do most tasks better than humans
D.
human workers often went on a strike when they were not satisfied in the past
【单选题】Do you think people will have robots ? [ ]
A.
at their homes
B.
in their home
C.
in their homes
D.
at homes
【简答题】How are service robots at home different from those in factories? [A] They perform. easier tasks. [B] They can work in small spaces. [C] They know human goals better. [D] They work closely with humans...
【简答题】《六一诗话》的作者是（）
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