为了解中国古代和谐社会的典范,小龙在学校图书馆借了一本《贞观政要》,他是为了探究下列哪一位皇帝的政绩?[ ]
A.汉武帝
B.唐太宗
C.唐玄宗
D.宋太祖
答案:B
管状侵蚀
An analyst does research about monopolistic competition. Which of the following statements is most accurate Long-run economic profit under monopolistic competition is zero because:()
A. entry into and exit from the market are possible with fairly low costs.
B. each firm produces a differentiated product.
C. two or more firms have the incentive to collude.