具有抗菌及扩张冠状动脉作用的是（）
A.紫草素
B.五味子素
C.柯桠素
D.番泻苷
E.丹参醌
参考答案：E
Would you please _________ the windows? It's cold now. [ ]
A. to close
B. close
C. closed
D. closing
简述风险避免的含义及其常用形态。
