以动物病理产物入药的药材是
A．珍珠
B．蝉蜕
C．石决明
D．牡蛎
E．五灵脂
参考答案：A
解析：珍珠以动物的病理产物入药。故答案选A。
______ is known to us all is that maths is one of the most difficult subjects. [ ]
A. As
B. That
C. It
D. What
泵壳由（）与（）组成。
