听力听写：

　　Slang

　　We often use slang expressions when we talk， because they are so vivid and colorful. However， they are usually out of place in formal writing/because of a number of drawbacks. / They go out of date quickly and become tiresome if used too much. / And they may communicate clearly to some readers but not to others./ In general， we should avoid the use of slang in our writing.

　　21.

　　A. opposed to

　　22.

　　D. personnel

　　23.

　　B. injured

　　24. C.yell

　　25. D、adaptable

　　26. A、 thoughts

　　27. C、to

　　28. B. arguably

　　29.D. specifically

　　30.A. enforcement