题干

由无理数引发的数学危机已知延续带19世纪,直到1872年,德国数学家戴德金提出了“戴德金分割”,才结束了持续2000多年的数学史上的第一次大危机.所谓戴金德分割,是指将有理数集Q划分为两个非空的子集M与N,且满足M∪N=Q,M∩N=∅,M中的每一个元素都小于N中的每一个元素,则称(M,N)为戴金德分割.试判断,对于任一戴金德分割(M,N),下列选项中不可能恒成立的是(  )

A:M没有最大元素,N有一个最小元素

B:M没有最大元素,N也没有最小元素

C:M有一个最大元素,N有一个最小元素

D:M有一个最大元素,N没有最小元素

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答案(点此获取答案解析)

C

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阅读理解

    Many musicians meet and form a band(乐队)because they like to write and play their own music.They may start as a group of high school students and practise their music in someone's house.Sometimes they may play to passers-by in the street or underground so that they can get some money for themselves or pay for their instruments(乐器).

    However,there was one band that started in a different way.It was called the Monkees and was formed in 1965.It began as a TV show.The TV show had planned to find four rock musicians who could act as well as sing.But they could only find one who was good enough.They had to use actors for the other three members of the band.

    Since some of these actors could not sing well enough,they had to ask for help from other musicians.So at first,the band just pretended(假装)to sing.Anyway,their performances(演出)were excellent and they got lots of fans.Each week on TV,the Monkees would pretend to play and sing songs written by other musicians.After a year or so,they became more serious about their work.They started to play and sing their own songs like a real band.Then they produced(制作)their own records and started touring and playing their own music.In the US they became even more influential and popular than the Beatles and sold even more records.

    However,the band broke up around 1970.But happily they reunited(重聚)in the 1980s.They produced a new record in 1996 to celebrate their time as a band.It was very successful.Today the Monkees are still making music for their millions of fans.

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