题干

如图a→d表示连续分裂细胞的两个细胞周期,下列叙述中不正确的是(  )

A:a和b为一个细胞周期

B:遗传物质平分一般发生在d段

C:b和c为一个细胞周期

D:c段结束DNA含量增加一倍

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C

同类题4

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    I live in the land of Disney, Hollywood. You may think people in such an attractive and exciting, fun-filled place are happier than others. If so, you have some mistaken ideas about the nature of happiness.

    Many intelligent people still consider happiness equal to fun. The truth is that fun and happiness have little or nothing in common. Fun is what we experience during an act. Happiness is what we experience after an act. It is a deeper, more lasting emotion.

    Going to an amusement park or ball game, watching a movie or television, are fun activities that help us relax, temporarily forget our problems and maybe even laugh. But they do not bring happiness, because their positive effects end when the fun ends.

    I have often thought that if Hollywood stars have a role to play, it is to teach us that happiness has nothing to do with fun. These rich, beautiful people have constant access to glamorous parties, fancy cars, expensive homes, everything that brings “happiness”. But in memoir after memoir, famous people expose the unhappiness hidden beneath all their fun — depression, alcoholism, drug addiction, broken marriages, troubled children and extreme loneliness.

    Ask an unmarried man why he refuses to get married even though he finds dating to be less and less satisfying. If he's honest, he will tell you that he is afraid of making a commitment. For commitment is in fact quite painful. The single life is filled with fun, adventure and excitement. Marriage has such moments, but they are not its most distinguishing features.

    Similarly, couples that choose not to have children are deciding in favor of painless fun over painful happiness. They can dine out whenever they want and sleep as late as they want. Couples with babies are lucky to get a whole night's sleep or a three-day vacation. I don't know any parent who would choose the word fun to describe raising children.

    The way people stick to the belief that a fun-filled, pain-free life equals happiness actually reduces their chances of ever achieving real happiness. If fun and pleasure are equal to happiness, then pain must be equal to unhappiness. As a result, they fear the pain unavoidably brought by such things as marriage, raising children, professional achievement, religious commitment and self-improvement.

    But, in fact, the opposite is true. More times than not, things that lead to happiness involve some pain. The very efforts are the source of true happiness. Understanding and accepting that true happiness has nothing to do with fun is one of the most liberating realizations we can ever come to.

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同类题5

阅读下文,回答相关问题。

                                                                                                      老海棠树
      ①奶奶和一棵老海棠树,在我的记忆里不能分开,奶奶一生一世都在那棵老海棠树的影子里张望。
      ②老海棠树近房高的地方,有两条粗壮的枝丫,弯曲如一把躺椅,小时候我常爬上去,一天一天地就在那儿玩。春天,老海棠树摇动满树繁花,摇落一地雪似的花瓣。我记得奶奶坐在树下糊纸袋,不时冲我唠叨:“就不说下来帮帮我?你那小手儿糊得多快!”我在树上东一句西一句地唱歌。奶奶又说:“我求过你吗?这回活儿紧!”我说:“我爸我妈根本就不想让您糊那破玩意儿,是您自己非要这么累!”奶奶于是不再吭声,直起腰,喘口气。这当儿,她就呆呆地张望——从粉白的花间,一直到无限的天空。
      ③或者夏天,老海棠树枝繁叶茂,奶奶坐在树下的浓阴里,又不知从哪儿找来补花的活儿,戴着老花镜,埋头于床单或被罩,一针一线地缝,天色暗下来时她冲我喊:“你就不能劳驾去洗洗菜?没见我忙不过来吗?”我跳下树,洗菜,胡乱一洗了事。奶奶生气了:“你们上班上学,就是这么糊弄?”奶奶把手里的活儿推开,一边重新洗菜一边说:“我就一辈子得给你们做饭?就不能有我自己的工作吗?”这回是我不再吭声。奶奶洗好了菜,重新捡起针线,从老花镜上沿抬起目光,又会有一阵子愣愣地张望。
      ④有年秋天,老海棠树照旧果实累累,落叶纷纷。早晨,天还昏暗,奶奶就起来去扫院子,“刷拉——刷拉——”,院子里的人都还在梦中。那时我大些了,正在插队,从陕北回来看她。那时奶奶一个人在北京,爸和妈都去了外地。那时奶奶腰弯背驼。“刷拉刷拉”的声音把我惊醒,赶紧跑出去:“您歇着吧,我来,保证用不了三分钟。”可这回奶奶不要我帮。“咳,你呀!你还不懂吗?我得劳动。”
      ⑤这样我才明白,她为什么执意要糊纸袋,要补花,不让自己闲着。有爸和妈养活她,她不是为挣钱,她为的是劳动。爷爷在旧社会是个地主,奶奶的成分也就随了爷爷算地主。文化大革命时,有人说爷爷在旧社会剥削农民,说奶奶是“吃了那么多年剥削饭!”这话让她无地自容,这话让她独自愁叹,这话让她几十年的苦熬忽然间变成屈辱。她要用行动证明。证明什么呢?她想她一定会有一天自食其力的。奶奶的心思我有点懂了:什么时候她才能像爸和妈那样,有一份名正言顺的工作呢?大概这就是她的张望吧,这就是那老海棠树下屡屡的迷茫和空荒。不过,这张望或许还要更远大些——她说过:得跟上时代。
      ⑥所有的冬天,在我的记忆里,几乎每一个冬天的晚上,奶奶都在灯下学习。窗外,风中,老海棠树枯干的枝条敲打着屋檐,摩擦着窗棂。一次,奶奶举着一张报纸,小心地凑到我的跟前:“这一段,你给我说说,到底什么意思?”我看也不看地就回答:“您学那玩意儿有用吗?您以为把那些东西看懂,您就真能摘掉地主帽子?”奶奶立刻不语,惟低头盯着那张报纸,半天半天目光都不移动。我的心一下子收紧,但知已无法弥补。“奶奶。”“奶奶!”“奶奶——”我记得她终于抬起头时,眼里竟全是惭愧,毫无对我的责备。
      ⑦在我的印象里,奶奶坐在满树的繁花中,满地的浓阴里,张望复张望,或不断地要我给她说说:“这一段到底是什么意思?”——这形象,逐年地定格在我的思念和我永生的痛悔之中。
                                                                                                                                                      (作者:史铁生 有删改)