题干

下列有关细胞有丝分裂和无丝分裂的叙述中,正确的是(  )

①在动物有丝分裂的间期能观察到由星射线形成的纺锤体   ②在植物细胞有丝分裂末期形成了细胞板   ③如果细胞中的染色体数:DNA数=1:2,它一定不是高度分化的细胞  ④有丝分裂过程中染色体加倍和染色单体的形成发生在同一时期  ⑤蛙的红细胞进行无丝分裂时,DNA不需要进行复制,而是细胞从中部向内凹陷,直接缢裂成为两个子细胞.

A:①③④

B:②④

C:①⑤

D:②③

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答案(点此获取答案解析)

D

同类题1

阅读下面短文, 从各题所给的A,B,C,D四个选项中选出最佳选项。

    One day, a teacher entered the classroom and told the students they would have a surprise test. After hearing that, all students were seated excitedly and waited for the test to begin soon. Then, the teacher gave the test papers to all students. However, the students were confused(困惑的)to see that there were no questions but just a black dot(点)in the center of the page. The teacher noticed the students' facial expressions and told them, "I want you to write about what you see there."

    The students were still confused but got started with the test. At the end of the class, the teacher took all the answer sheets and started reading each answer in front of all students. All of them described about the black dot and tried to explain its position. After the teacher finished reading, the whole class was silent.

    Then, the teacher began to explain. "Don't worry. I am not going to give you grades for this, but I just want you to think about something. Here everyone focused(聚焦)on the black dot and wrote about it, but no one wrote about the white paper, the same is with our lives. The white paper represents(象征)our whole life and the black spot represents problems in our life."

    Our life is a gift given to us by God, with love and care, and we always have reasons to celebrate-our friends around us , the job that provides us with livelihood , the miracles(奇迹)we see every day. Still we just focus on day to day problems like health issues, lack of money, problems in relationships and so on, but we never see that these problems are very small, compared to everything we have in our lives. So we should try to be happy and live life positively.

同类题5

任务型阅读

    Looking back on the first twenty years of my life,I feel grateful to have been so healthy and happy.I'm happy because of many key factors(因素).____

    Health comes first for me, because without health everything else is meaningless. Imagine starting a career without good health. Imagine achieving anything without good health.____

    Good health is not enough to be happy.____Money obviously pays for the basic necessities of life—food, housing, clothing, etc.—but it is also necessary for other reasons. Money guarantees(保证) we always get good medical treatment when we fall ill. Besides, we can also use money for entertainment that can add to our quality of life.

    Family is another important factor in having a happy life because it provides the love, joy, and support that everyone needs. I love my family with all my heart. I get pleasure from their pleasure. I suffer when they suffer.____ They give me advice when I have misunderstandings with my friends. More importantly, they are always there to share everything with me.

    ____ As long as I stay healthy, work hard to earn enough money and share both good times and bad times with my family,I will always be the happiest girl in the world.

A. Money is the most important factor which contributes to a happy life.

B. These three factors are all that I need and want in this world.

C. My family help me get through worries, pressures and difficulties.

D. We still need to have money in today's society.

E. Finally, I'm quite thankful that I am healthy, wealthy and happy.

F. Clearly, good health is much more important than any other things of one's life.

G. They include my physical health, healthy finances and my family's happiness.