试述保证的免除和消灭。

阅读理解。

      Mr. Smith is an American man. He teaches us English. He is a very good teacher and we all like him. He

likes us, too.

      Mr. Smith has two children — Tom and Mary. Tom is seven and his sister, Mary, is four. Tom goes to

school, but Mary doesn't. Mr. Smith likes wearing (穿) a T-shirt and jeans (牛仔裤). Soccer is his favorite

sport. After school we often have a baseball match. Sometimes Mr. Smith watches and joins us. He plays

baseball just for fun.

1. We like Mr. Smith because (因为) _______. [ ]

A. he is an American man

B. he teaches English

C. he is a good English teacher

2. How many sons does Mr. Smith have? [ ]

A. Only one.

B. Two.

C. Three.

3. Mary doesn't go to school because ______. [ ]

A. she is Tom's sister

B. she is only four.

C. she doesn't like school.

4. ______ is Mr. Smith's favorite sport. [ ]

A. Baseball

B. Soccer

C. Volleyball

5. The story (故事) is about ______. [ ]

A. Mr. Smith

B. Mr Smith's children

C. Mr Smith's sports

读图，回答问题．

（1）写出图中字母代表的地形部位名称．

A：______     B：______  C：______  D：______   E：______

（2）图中小河F的流向是______，用箭头在图中标出．

（3）甲、乙两山顶之间的实地距离是______米．

（4）山顶甲在山顶乙的______方向．

（5）甲山顶的海拔是______米，甲、乙两山顶的相对高度是______米．

（6）E处与D处相比，坡度较缓的是______处，原因是______．

上市公司应当在可转换公司债券期满后10个工作日内，办理完毕偿还债券余额本息的事项。()

在财产保险理赔中，如果保险事故是由第三者的行为引起，保险人按照保险合同的约定或法律规定，在对被保险人的索赔请求先行赔付后，被保险人将向第三者追偿的权力转让给保险人，这种权力属于()。

A.物上代位权

B.赔偿请求权

C.代位求偿权

D.损失索赔权

The fiddler crab (蟹) is a living clock. It shows the time of day by the colour of its skin, which is dark by day and pale by night. The crab’s changing colour follows a regular twenty—four hour plan that exactly matches the daily rhythm of the sun.

Does the crab actually keep time, or does its skin simply answer to the sun’s rays, changing colour according to the amount of light strikes it? To find out, biologists kept crabs in a dark room for two months. Even without daylight, the crab’s skin colour continued to change exactly on time.

This characteristic probably developed gradually in answer to the daily rising and setting of the sun, to help protect the crab from sunlight and enemies. After millions of years it has become completely regulated (受控制) inside the living body of the crab.

The biologists noticed that once each day the colour of the fiddler crab is especially dark, and that each day this happens fifty minutes later than on the day before. From this they discovered that each crab follows not only the rhythm of the sun but also that of the tides (潮水). The crab’s period of greatest darkening is exactly the time of low tide on the beach where it was caught!

小题1:The fiddler crab is like a clock because it changes colour ______.

A in a regular 24—hour rhythm              B. in answer to the sun’s rays

C. at low tide                            D. every fifty minutes

小题2:The crab’s changing colour ______.

A．tells the crab what time it is

B．protects the crab from the sunlight and enemies

C．keeps the crab warm

D．is of no real use小题3: When the fiddler crabs were kept in the dark , they ______.

A．did not change colour

B．changed colour more quickly

C．changed colour more slowly

D．changed colour on the same timetable小题4:The crab’s colour—changing ability was probably developed ______.

A．in the process of evolution (进化)

B．over millions of years

C．by the work of biologists

D．both A and B小题5:The best title for this selection would be ______.

A．The Sun and the Tides

B．Discoveries in Biology

C．A scientific Study

D．A Living Clock