试题与答案

当正整数a,b满足什么条件时对于任意x∈Zn*,有xab=x?()A、ab≡4(mo

题型:单项选择题

题目:

当正整数a,b满足什么条件时对于任意x∈Zn*,有xab=x?()

A、ab≡4(modφ(m))

B、ab≡3(modφ(m))

C、ab≡2(modφ(m))

D、ab≡1(modφ(m))

答案:

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参考答案:食管约25cm。①食管与咽相续处,15cm。②左主支气管与食管交叉处,25cm。③食管穿过膈食管裂孔处,40cm。

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题型:阅读理解

     During the 19th century, it was common to hear people in Europe and America say that the

resources of the sea were unlimited. For example, a noted biologist writing in the mid-19th century

commented that none of the great sea fisheries(渔业) are to be exhausted. Today though, there is

evidence that the resources land and the air,  and that the endangered species (种类) include Herring

and Carp as well as the African Elephant, Indian Tiger, and the American Eagle.

     Further, the threats to fish are more alarming in some ways than the threats to animals and birds.

     This is because fish are a much needed food resource and people throughout the world depend on

fish as an important part of their dish,  and the decline (下降) in the fish supply could have extensive

effects on hunger and population.

     Fishermen in the North Atlantic alone annually harvest 20 billion pounds of fish to satisfy food

demands, but it is important to recognize that these practices cannot continue without depleting (耗尽)

fish storage within the next few years. Sea resources are rapidly declining in many parts of the world,

and the problem cannot he ignored (忽视) .

     We can predict that food supplies in the sea can not last forever.

1. According to the speaker, what was the attitude(态度) in the 19th century toward resources of

the sea?

A. Declined.              

B. Depleted.

C. Limited.                

D. Unlimited.

2. What is the range(地带)  of the decline in fish supply?  

A. Europe and Asia.        

B. The whole world.

C. Asia and America.      

D. America.

3. What does the author believe about sea resources?   

A. Sea resources can last forever.

B. None of the great sea fisheries are to be exhausted.

C. Fish supply has no effects on people.

D. Sea resources are important to people.

4. Which of the following best describes the purpose of the lecture?

A. Unlimited Sea Resources

B. Threats to Animals and Birds

C. Sea Resources on the Decline

D. Protection of Fish

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