问题 单项选择题

下列关于抛射剂的叙述错误的是()

A.抛射剂可分为压缩气体与液化气体

B.压缩气体常用作喷雾剂动力

C.抛射剂在气雾剂中起到动力作用

D.抛射剂可兼作药物的溶剂或稀释剂

E.气雾剂喷雾粒子大小、干湿与抛射剂用量无关

答案

参考答案:E

解析:抛射剂是气雾剂的组成部分之,它有时也可作为主药的溶媒或稀释剂,抛射剂的性质和用量与气雾剂雾粒大小、干湿等有关。抛射剂可采用压缩气体如氮、二氧化碳或氧化亚氮等,但现在大多采用氯烷烃类等沸点低于室温的液化气体,如三氯一氟甲烷、二氟甲烷、三氯四氟乙烷等。如单使用一种氟氯烷烃类抛射剂效果不满意时,可将两种或更多的氟烷烃类混合制成需要蒸汽压的混合抛射剂。

单项选择题 A1/A2型题
单项选择题

When I first entered university, my aunt, who is an English professor, gave me a new English dictionary. I was (16) to see that it was an English-English dictionary, also known as a monolin-gual dictionary. (17) it was a dictionary intended for non—native learners, none of my classmates had one (18) , to be honest, I found it extremely (19) to use at first. I would look up words in the dictionary and (20) not fully understand the meaning, I was used to the (21) bilingual dic-tionaries, in which the words are (22) both in English and Chinese, I really wondered why my aunt (23) to make things so difficult for me. Now, after studying English at university for three years, I (24) that monolingual dictionaries are (25) in learning a foreign language.

As I found out, there is (26) often NO perfect equivalence(对应) between two (27) in two language. My aunt even goes so far as to (28) that a Chinese "equivalent" can never give you the (29) meaning of a word in English! (30) , she insisted that I read the definition(定义) of a word in a monolingual dictionary (31) I wanted to get a better understanding of its meaning. (32) , I have come to see what she meant.

Using a monolingual dictionary for learners has helped me in another important way. This dictionary uses a(n) (33) number of words, around 2,000, in its definitions. When I read these definitions, I am (34) exposed to (接触)the basic words and learn how they are used to explain objects and ideas. (35) this, I can express myself more easily in English.

20()

A. thus

B. even

C. still

D. again