香豆素母核为
A．苯骈-α-吡喃酮
B．对羟基桂皮酸
C．反式邻羟基桂皮酸
D．顺式邻羟基桂皮酸
E．苯骈-γ-广吡喃酮
参考答案：A
________the help of the teacher, the student who wasn't good at math________the difficult problem
quickly.[ ]
A. Under; worked out
B. With; worked on
C. Under solved
D. With; solved
企业可利用知觉图来分析和了解（）与（）关系，并基于产品属性来更好地描述现有产品或品牌在整个市场中所处的地位，同时为新品牌明确定位。
