单项选择题 已知某消费者的月收入为9000元，全部花费于X和Y两种商品，他的效用函数为U＝2XY，X的价格是30元. Y的价格是40元。 为使效用最大，他应该购买的X和Y各为

不定项选择 新时期最鲜明的特点是发展生产力。

单项选择题 Which of the following quotations seeks to establish goodwill? A、The which if you with patient ears attend, / What here shall miss, our toil shall strive to mend. B、For your voices I have fought; / Watch’d for you voices. C、I have been studying how I may compare / This prison where I live unto the world. D、Good Ursula, wake my cousin Beatrice, and desire her to rise.