已知盐水若干克，第一次加入一定量的水后，盐水浓度为3%；第二次加入同样多的水后，浓度
题型：单项选择题
问题：
已知盐水若干克，第一次加入一定量的水后，盐水浓度为3%；第二次加入同样多的水后，浓度变为2%，那么第三次加入同样多的水后盐水的浓度为( )。
A．1.6%
B．1.5%
C．1.2%
D．1%
题型：单项选择题
阅读理解。
Endangered languages are languages that wouldn't exist any longer, much like endangered species of
plants or animals. Languages are considered to be endangered when parents are no longer teaching the l
anguage to their children and are not using it actively in everyday life. A language is considered to nearly
disappear when it is spoken by only a few elderly native speakers.
The world faces enormous challenges in order to protect different kinds of languages. Of the more than 6,912 languages, half may be in danger of disappearing in the next several decades.
It is caused by many reasons: small numbers of speakers, the regular use of other languages, attitudes
towards their languages, moving of the younger population, government policies, and languages used in
education and so on. A language may lack important things such as a body of literature, and people who
read and write it. A language may also lack prestige (声望) and support of its speakers.
The survival of a language is also threatened when speakers move to other areas where different
languages are spoken, or when government policies improve the use of a specific language in school,
official business and the media. These situations encourage people to learn the wider-known language
and may cause them, especially the young, to stop using their mother tongue. Often those speaking
lesser-known languages will choose to learn a more prestigious language with the hope of greater
economic opportunities. Most of the world's parents are teaching their children English, French, Spanish,
Chinese, Arabic, Russian or some other main languages instead of their own languages for social and
economic reasons.
1.What's the main idea of this passage?
A. Languages in the world.
B. Reasons why languages become endangered.
C. What an 
endangered language is.
D. Languages spoken by few speakers.
2. About ________languages will probably disappear in this century according to the passage.
A. more than 6,912
B. more than 3,456
C. 6,912
D. less than 3,456
3.Which of the following best shows the structure of the passage?
①=Paragraph1②=Paragraph2 ③=Paragraph3 ④=Paragraph4
4.We can infer that the best way to maintain an end
angered language is to _________.
A．forbid the speakers to move about
B．pass laws to protect the language
C．raise the salaries of the people who speak the language
D．teach the language to young ch
ildren and encourage people to speak it often
5.All of the following about languages are true EXCEPT __________.
A．many languages will be probably endangered in this century
B．government policies have a big effect on languages
C．the endangered language is a language that is spoken by a few people
D．languages are relat
ed to their speakers' social 
and economic position