题干

某同学在做“观察蝗虫精母细胞减数分裂固定装片”实验中,下列表述不正确的是(   )

A:先用低倍镜找出各时期的细胞

B:在高倍镜下能观察到染色体的形态和数目

C:能观察到减数第一次分裂中期有姐妹染色单体

D:能观察到减数第二次分裂中期有同源染色体来源:学§科§网

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答案(点此获取答案解析)

D

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阅读理解

    It is quite reasonable to blame traffic jams, the cost of gas and the great speed of modern life, but manners on the road are becoming horrible. Everybody knows that the nicest man would become fierce tigers behind the wheel. It is all right to have a tiger in a cage, but to have one in the driver's seat is another matter.

    Road politeness is not only good manners, but good sense. It takes the most cool-hearted drivers great patience to give up the desire to beat back when forced to face rude driving. On the other hand, a little politeness goes a long way towards reducing the possibility of quarrelling and fighting. A friendly nod or a wave, or thanks in answer to an act of politeness helps to create an atmosphere of good will and becomes so necessary in modern traffic conditions. But such behaviors of politeness are by no means enough. Many drivers nowadays don't even seem able to recognize politeness when they see it.

    However, misplaced politeness can also be dangerous. Typical example is the driver who waves to a child crossing the street at a wrong place into the path of oncoming cars that may not be able to stop in time. The same goes for encouraging old ladies to cross the road wherever and whenever they want to.

    An experienced driver, whose manners are faultless, told me it would help if drivers learnt to correctly join in traffic stream without causing total jams that give rise to unpleasant feelings. Unfortunately, modern drivers can't even learn to drive, let alone master the roadmanship(驾车技能). Years ago, experts warned us that the fast increase of the car ownership would demand more give-and-take from all road users. It is high time that all of us took this message to heart.