题干

下列对菠菜根的分生区细胞分裂过程的叙述中,正确的是(  )

A:在DNA复制的时期,DNA和染色体的数目增加一倍

B:在核膜和核仁消失后,中心体发出星射线形成纺锤体

C:在染色体形态固定、数目清晰的时期,着丝点排列整齐

D:在染色体逐渐解开螺旋的时期,细胞中央出现由细胞壁构成的赤道板

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答案(点此获取答案解析)

C

同类题5

阅读下文,然后从各顺所给的四个选项中选出一个最佳答案.

    Technology is everywhere. We see it any place we go and, in fact, almost all of us carry some piece of technology with us every time we leave the house. What I always forget, though, is just how useful and powerful technology can be when we want to help others.

    There is not a single room in my house that does not have some electronic devices(设备)lying around in it. Whenever I am at home, I am almost always using at least one electronic device. If you walked into my living room on any given day, you would find that, first, I have the television on. At the same time, I usually have my laptop resting on my knee, or I will be using my mobile phone. Even when I'm not at home I am always using my phone, and at work or in cafes, I sit down and connect to the local wireless network on my laptop.

    I must say that I waste a lot of time on the computer and the time I spend on it could be much better spent if I were to take up a little online volunteering.

    The technology we carry about everywhere can have a great power to do good for the world and to help others and recently I discovered just how much online volunteering there is to do in the world. From using your language skills to do translations, to developing and managing projects and helping with IT work, there is so much that so many people can do to help people in their own countries and across the world. The United Nations, in fact, has a huge page with "Volunteers Recruited" on its website.

    This work can support the poor and help charities who cannot pay for staff. Many organizations only require you to work an hour a week-some even less. And the support provided by online volunteers can really help make a difference to those in need.