市场分割理论具有明显的缺陷,持这种观点的投资者越来越少。()
参考答案:对
—______ did you stay in the USA?
—For about ten years. [ ]
A. How long
B. How often
C. How soon
D. How old
属于苯丙胺类生物碱的是()
A.秋水仙碱
B.阿托品
C.可待因
D.苦参碱
E.麻黄碱