下列有关白喉外毒素特点描述错误的是（）

A.为不耐热的多肽

B.毒力强

C.可阻碍细胞蛋白质合成

D.能刺激机体产生抗毒抗体

E.经0.5％甲醛处理成为类毒素

补全对话 （有一项是多余的）

Daming="D;" Tony=T

D: How long have you studied Chinese?

T:小题1:        

D: Really? Your Chinese is pretty good!

T: But, I don’t think Chinese is easy to learn.小题2:          

D: In 2000. It has been 6 years.

T:小题3:           

D: Well, my grammar and vocabulary are good.小题4:           

T: You should often listen to English music and see English films.

D:小题5:          

T: Sure, they do!

A．Do you find it difficult to learn English?

B．By the way, when did you start to learn English?

C．For more than two years

D．But my listening is not very good.E. Do they work? F. Thanks a lot.