It may seem easy to say that plants and animals are different. Any child can tell the difference between  a tree and a dog. But those differences are far deeper than just what they look like. The cells (细胞) that plants are made up of are different. In other words, the cell wall of plants has something special.

First of all, it's important to find that not all plant cells have a cell wall. Besides, there are many differences of a cell wall based on the kinds of plant. The following is meant to be what a plant cell wall is  like.

  The cell wall of a plant is on the outside of the cell membrane (膜). It is usually hard and cannot be bent easily, but the degree of flexibility (韧性) of the cell wall is different. It is based on the special use that the cell has in keeping the plant alive. Cells that make up the trunk of a tree are clearly less flexible than? cells on a leaf.

     Cell walls act in many ways. They serve to protect the plant. They provide support, as well as help in the movement of chemicals and wastes into and out of the cell.  More importantly, they control the water? that goes in and out.  Plants must have good water controlling systems (系统), allowing them to keep water during dry seasons, and get rid of unnecessary water. Plants can't walk around to find water, so  being able to control water is very important.

So there you have it , what a plant cell wall is. Of course, there are many other things that are not talked about here. Knowing more about plant cell wails requires further study and research.

1.From the first two paragraphs we can find that _____.

A. all plants have a ceil wall?????????????

B. plant cells and animal cells are the same

C. different kinds of plant have different cell walls

D. there are no differences between the cells of a tree and a dog

2.The underlined word "bent" in the passage is the closest in meaning to _____.

A. 变形的 ?? B. 防水的   ? C. 太阳灼伤的     ??? D. 表皮破损的

3.Cells in the trunk of a tree are _____ those on a leaf.

A. as flexible as             ?????????  B. not so flexible as

C. more important than                ?? D. less important than

4.What is the most important use of a plant cell wall?

A. To protect the plant.                ???? B. To provide support.

C. To move chemicals and wastes.       D. To control the water.

    Englishmen speak British English and Americans speak American English. A student is learning to speak British English. He often asks himself, “Can Americans understand me when I speak British English?” Certainly there are some differences between British and American English. The Englishmen say “Do you have a pen?” The pronunciation is sometimes different. Americans often sound “r” in words like “bird” and “hurt”. The British speakers don’t sound the “r” in these words. There are differences in spelling. For example, “colour” and “neighbour” are British while “colour” and “neighbour” are American. These differences in grammar, pronunciation and spelling are not important, however. For the most part, British and American English are the same language. When Englishmen and Americans are talking with each other, the don’t need an interpreter(翻译).

1．Between British and American English, _______

A．the greatest difference is in spelling

B．there are differences in many ways

C．people can’t understand each other      D．students don’t know the difference

2. When a student is asking himself “Can Americans understand me when I speak British English?” it shows that_______.

A. he wants to learn American English                 B．he doesn’t like British English

C．he hasn’t spoken to any American so far   

D．he is spending more time

3. The differences between British and American English are not important because______

A. everyone knows the differences 　　

B. people talk to each other very often

C. Englishmen and Americans get along well    

D. British English and American English are the same language

4. “Have you a pen” and “Do you have a pen?” show a difference in______

A. grammar                  B. spelling 

C. pronunciation            D. listening

5. At the end of the passage the writer wants to tell us _______.

 A. British and American English will be two different languages some day

 B. Englishmen and Americans will never need an interpreter while talking

 C. there will be no more differences between British and American English

 D. the differences between British English and American English will grow larger