二尖瓣狭窄和主动脉瓣狭窄并存时，二尖瓣狭窄常会掩盖主动脉瓣狭窄的临床表现。
参考答案：错
An average of just 18.75cm of rain fell last year, making ______ the driest year since California became a state in 1850.
A．each
B．it
C．this
D．one
既能止咳平喘，又能润肠通便的药物是（）
A.瓜蒌仁
B.葶苈子
C.柏子仁
D.杏仁
E.栀子
