主要成分为甾体皂苷的是（）
A.秦皮
B.麦门冬
C.大黄
D.乌头
E.厚朴
参考答案：B
________ a lot of trees in this area, but now we can see a tall building instead.
A．There used to have
B．There used to be
C．There is used to having
D．There is used to being
在X线摄影中，光电效应的负面影响是
A．产生散射B．产生灰雾C．增加X线对比度D．使病人接受的照射量多E．以上四项都是
