代谢产物M-6葡糖苷酸有镇痛活性的药物是（）。
A.哌替啶
B.芬太尼
C.吗啡
D.曲马朵
E.安乃近
参考答案：C
The book __ __by the young writer sells well. It is popular among middle school students.
A．was written
B．writing
C．wrote
D．written
肾盂切开取石术适用于大于_____cm的结石，或合并________、_______的结石。
