问题 单项选择题

(三) 危险化学品安全生产技术

海上油气田火灾及可燃气体控制器种类过多,一般在同一场所使用两种控测器进行探测,一个探测动作就进行报警,两个同时动作可触发消防系统启动。当探测器探测的浓度达到爆炸浓度低限的( )时就分别开始预报警和报警。

A.20%和60%

B.10%和40%

C.20%和50%

D.10%和30%

答案

参考答案:A

阅读理解

阅读理解。

     What are your hobbies? Many children like stamp-collecting in their spare time. Do you know? Stamp

collecting didn't start until 1854.   As time passes,  there are more  and more  stamp-collectors.  Not only

children  but  also  men  and women are  collectors.   In some countries,  there are even lessons  on stamp

collecting in school. People are becoming more and  more interested  in stamps.  Every picture on a stamp

has its meaning in it.  It may be the head of a famous person,  an important place or special moment.  Each stamp tells us a story.   We can learn  a  lot  from stamps.   Now  stamp-collecting is my favourite hobby.  

Why not join us?          

1. Stamp-collecting started___________.

A.  earlier than 1845                

B.  later than 1921

C.  in 1854                        

D.  hundreds of years ago

2. Stamp-collectors are___________.

A. men and women                

B.  boys and girls

C.  neither young nor old          

D.  both A and B

3.  Lessons on stamp-collecting are given in___________.

A. a few countries  

B.  few countries  

C.  our country  

D.  America only

4. There are more and more stamp-collectors. This sentence means           

A. people are collecting different kinds of stamps

B. the number of stamp-collectors is growing

C. a group of people are collecting stamps

D. more and more stamps are being printed

5. Every picture on a stamp __________.

A. is the head of a stamp-collector

B. tells us something interesting

C. has nothing to do with America

D. tells us a story about some schools

单项选择题