入汤剂需先煎的药物是（）
A.薄荷、豆蔻
B.蒲黄、海金沙
C.人参、阿胶
D.磁石、牡蛎
E.以上均不是
参考答案：D
简述社会变迁的主要类型。
The length of the steering oar in a lifeboat is（）.
A.shorter than the rowing oars
B.the same length as the rowing oars
C.longer than the rowing oars
D.unrelated to the length of the rowing oars
