题干

在减数第一次分裂后期,父方和母方的染色体如何移向细胞两极    (  )

C:父方和母方染色体中各有一半移向一极,另一半移向另一极

A:父方和母方染色体在两极随机地组合

B:通常母方染色体移向一极而父方染色体移向另一极

D:未发生交叉互换的染色体移向一极,而发生交叉互换的染色体移向另一极

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A

同类题5

阅读理解

    You're rushing to work and a man ahead of you collapses (跌倒) on the sidewalk. Do you stop to help? In a study of by-standers, it was found that some people avert their gaze and keep on walking rather than stop and get involved. “There is a tendency to decide that no action is needed.” says a psychologist. “The first thoughts that pop into (进入) your mind often keep you from offering help. In order to take action, you have to work against them.” Here are some common thoughts that might prevent you from helping.

    Why should I be the one? I'm probably not the most competent (有能力的) person in this crowd. You might think someone older or with more medical knowledge should offer assistance (帮助).

    What if he doesn't really need my help? The fear of embarrassment is powerful; no one wants to risk looking foolish in front of others.

    No one else looks concerned-this must not be a problem. We can follow the people around us, but most  people tend to hold back their emotions in public.

     “If you spot (发现) trouble and find yourself explaining inaction, force yourself to stop and evaluate the situation instead of walking on,” says the psychologist. “Then retry to involve other people; you don't have to take on the entire responsibility of being helpful. Sometimes it's just a matter of turning to the person next to you and saying, “It looks like we should do something.” Or asking someone if an ambulance has been called and, if not, to call for one. Once you take action, most people will follow you.”