将参加夏令营的500名学生编号为：001,002，…，500，采用系统抽样的方法抽取一个容量为50的样本，且随机抽得的号码为003，这500名学生分住在三个营区，从001到200在第一营区，从201到355在第二营区，从356到500在第三营区，三个营区被抽中的人数为( )
A．20,15,15
B．20,16,14
C．12,14,16
D．21,15,14
答案：B
根据系统抽样特点，被抽到号码l＝10k＋3，k∈N．第353号被抽到，因此第二营区应有16人，所以三个营区被抽中的人数为20,16,14．
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| How would you like to go to a school like this one in Oxford, England? There are no formal classes. The students 1 from one group to another when they want to. 2 may find students who are fourteen, fifteen or sixteen years old all in the same 3 . They work at their own speed. 4 tells them what they should or shouldn't be doing. The day I 5 , school began at nine. Some students were working 6 a tape recorder and listening to their own voices. Others were watching a TV program 7 physics. A third group was working in the library. I didn't see anybody just sitting doing 8 . Nobody was wasting time. 9 the students taking a break in the cafeteria were having a 10 on politics (政治). | ||||
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