二尖瓣狭窄( )
A.最易出现周围血管征B.最易发生咯血C.最易引起左心房和左心室同时增大D.最易发生晕厥和心绞痛E.最易发生右心室增大
参考答案:B
I don't think teenagers should be allowed to drive, because they are _____.
A. not enough serious
B. not serious enough
C. too serious
D. to serious
波浪冲击闸门,使闸门振动常发生如汽笛响声的呜音。