题干

下列有关“观察根尖分生组织细胞的有丝分裂”实验过程叙述正确的一组是( )

①解离的目的是用药液使组织细胞相互分离

②漂洗的目的是洗去根尖上的解离液

③压片的目的是使根尖细胞分散开来

④应选取长方形的细胞进行观察

⑤可以持续观察一个细胞,认识有丝分裂的完整过程

A:①②③

B:③④⑤

C:①④⑤

D:②③④

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答案(点此获取答案解析)

A

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     People have been raising pigeons(鸽子) for about 10,000 years. And pigeon  keepers use  different kinds of pigeons for different 1Some people use pigeons for 2 For example, in parts of China people cook a special meal with pigeon to celebrate the New Year.

Some people also keep pigeons because they look especially 3There are many interesting kinds of these “pretty” pigeons. Different kinds of pigeons have interesting features 4 long, soft tail feathers or designs on their heads. The owners of these kinds of pigeons enter them in 5  and the best looking pigeons are chosen to win prizes.

     But pigeons have many othe6   too. Pigeons can fly long distances without growing 7 . They also have another8sense. No matter how far from home they are, pigeons can usually fly back to where they9This is often called a “homing sense”. This sense makes them good for carrying10

     In many cities around the world, pigeons live in special houses, and pigeon keepers spend a lot of money and time11 their birds. When someone has a very good pigeon, he is very12    He may also have a way to make money.  But this is not usually the main13 people keep pigeons. For some people, they keep pigeons as a hobby.

     People love pigeons so much that they even take them14 when they move to a new country. They15 these birds as their children.  “When you are looking at a pigeon in the sky you feel free. It is the best feeling you have in a strange country”, a pigeon lover says.