一个多边形的内角是1440°，求这个多边形的多数是（） A．7 B．8 C．9

下列属于气雾剂阀门系统组成部件的是（）。

A、药物

B、抛射剂

C、附加剂

D、橡胶封圈

Students in many countries are learning English. Some of these students are small children. Others are teen-agers. Many are adults. Some learn at school, others by themselves. A few learn English by learning the language over the radio, on TV, or in film. One must work hard to learn another language.

Why do all these people want to learn English? It is difficult to answer this question. Many boys and girls learn English at school because it is one of their subjects required for study. They study their own language and maths and English: Some people learn it because it is useful for their work. Many people learn English for their work. Many people learn English for their higher studies, because at college or university some of their books are in English. Other people learn English because they want to read newspapers or magazines in English.

小题1:People learn English _______.

A．at school

B．over the radio

C．on TV

D．not all in the same way小题2:Different kinds of people want to learn English _______.

A．together with other subjects

B．for different reasons

C．for their work

D．for higher studies at colleges小题3:From this passage we know that _______.

A．we can learn English easily

B．English is very difficult to learn

C．English is learned by most people in the world

D．English is a useful language but one must work hard to learn小题4:Which of the following is right?

A．We don’t need to learn any foreign languages.

B．We can do well in all our work without English.

C．English is the most important subject in schools.

D．We should learn English because we need to face the world.

20世纪50年代，美国干涉中国内政最严重的事件是 [ ]

A、侵略朝鲜

B、派第七舰队到台湾，阻止中国解放台湾

C、将战火烧到鸭绿江边

D、敌视中国

使用冷回流控制分馏塔顶温度注意什么？

PY180平地机工作装置的液压油缸和液压马达采用（）。

A、两个都是双作用

B、两个都是单作用

C、前单后双

D、前双后单