题干

下列关于有丝分裂的叙述,错误的是(  )

A:间期染色质完成复制后数目加倍

B:中期染色体缩短到最小程度,便于观察和研究

C:后期移向两极的染色体形态和数目完全相同

D:有丝分裂是真核生物进行细胞分裂的主要方式

上一题 下一题 0.0难度 选择题 更新时间:2018-09-07 04:56:52

答案(点此获取答案解析)

A

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阅读理解

    27 world records were broken during the 2016 Summer Olympics. They fell in swimming running weightlifting and a number of other sports. But how do athletes continue to get better, jump longer, run or swim faster? Although scientists say that athletes have reached their limits (极限), records continue to fall. In almost every sport, athletes have become better since the Olympic Games begin.

    One reason is that and more people than ever before have access to sports and exercise. They start at an earlier age and can compete longer in their sport. In schools more and more natural talents can be discovered.

    Besides, athletes can train full-time instead of training after works. As medicine improves, athletes can stay in competition for a longer time and overcome injuries (损伤) faster. Many top athletes achieve their best results later on in their careers. Technology has also helped improve scores.

    One of the most important reasons, however, is the human mind. We always want to be better and faster that someone else. It can release (释放) great power in our body.

    So, where are limits? One of the most difficult questions to answer is how fast a human being can run. Many years ago, nobody thought a person could ever run within 10 seconds in the 100-metre race. But the record was broken at the 1968 Mexico City Olympics. A t the moment Sustain Bolt is the fastest man on Earth at 9.58 seconds. Scientists say that 9.48 may be the limit, but, who knows, maybe some runners will one day run within 9 seconds.