要达到N个经济目标，至少需要N种独立的政策工具，这被称为（ ）。

(单选题)截止2016年6月30日，平均每个美团商家有多少外卖用户？（ ） (单选题)Had Judy been more careful on the maths exam, she ( ) mu (单选题)Soon after getting off his horse, the captain appeared at th (单选题)The government has promised to do ( ) lies in its power t (单选题)( ) should not become a serious disadvantage in life and w (单选题)James has just arrived, but I didn’ t know he ( ) until y (单选题)Fred entered without knocking and, very out of breath, sank (单选题)A great man shows his greatness ( ) the way he treats lit (单选题)I like Mr. Miner's speech; it was clear and ( ) the point (单选题)To my horror, I saw, ( ) my father's shoulder, a gorilla.