问题 单项选择题

()的作用是在操作到危险点之前,自动使机器停止或反向运动。

A.控制安全装置

B.自动安全装置

C.跳闸安全装置

D.自动调节安全装置

答案

参考答案:C

解析:

本题考核的是跳闸安全装置的作用。跳闸安全装置的作用,是在操作到危险点之前,自动使机器停止或反向运动,该类装置依赖于敏感的跳闸机构,同时也有赖于机器能够迅速停止(使用刹车装置可以做到这一点)。为使机器能迅速地停止运动,可以使用控制装置。自动安全装置的机制是把暴露在危险中的人体从危险区域中移开,仅限于在低速运动的机器上采用。自动调节装置由于工件的运动而自动开启,当操作完毕后又回到关闭的状态。

阅读理解

阅读理解。

     Have you ever wondered what kinds of music young people across the United States are listening

to?  Are they crazy about Britney Spears? Do they love the Backstreet' Boys? Or do they dance with 

Eminem?  

     Well, nearly 6000 teens have taken part in a Teen & Music survey, made by USA Weekend

Magazine last autumn. And the result showed what types of music are hot and what are not.   

     It comes without surprise that hip-hop and rap are the most popular types of music among

American teenagers. They began in the mid-1970s with young black kids in New York, taking music

onto the streets. Hip-hop' and rap are well known for the break-dancing that goes with them.

     The word "rap" comes from a slang word. It is a rapid thyme that is spoken rather than sung.

Pop music, such as Britney Spears and the Backstreet Boys, has always met the tastes of the general 

public. It continues to enjoy support from teens and is the second most popular music after

hip-hop and rap.  

     The third is rock music with exciting dance beats and simple lyrics that speak loudly of social

problems. The melodies are led by electric guitars. Rock became popular in the US in the early 1950s.

The American singer Elvis Presley and British group the Beatles became world famous rock artists.

     The survey also showed that jazz is least loved by American teens. It developed in the later part of

the 19th century from a mixture of African work songs and hymns. Jazz tends to be the type of music

that people enjoy more as they get older. 

1. The Teen & Music survey was made by ____.

A. teenagers

B. teens        

C. USA Weekend Magazine

D. Backstreet Boys 

2. American teenagers like ____ best.        

A. hip-hop and rap

B. pop music        

C. rock music

D. jazz  

3. Britney Spears and the Backstreet Boys belong to ____.        

A. pop music

B. hip-hop        

C. rock music

D. jazz 

4. In the later part of the 19th century ____ developed.

A. rap

B. jazz    

C. the Beatles

D. the electric

5. This passage mentions at least ____ kinds of music in America.    

A. three

B. four    

C. five

D. six

单项选择题