A．Its scarce proteins.
B．Its terrible taste.
C．Its many vitamins.
D．The difficulty of finding it.

单项选择题假如Qx=20-0.5Px+0.1I-2.0Py，Py=2和Qx=10，那么x的交叉弹性为： A．-0.2 B．-0.4 C．-0.04 D．0.4

单项选择题假如Qx=20-0.5Px+0.1I-2.0Py，物品x和物品y为： A．替代品 B．互不相关 C．低档货 D．互补品

未分类题A．look upB．look downC．look awayD．lo0k back

未分类题听力原文：W: Hey! The train is late! I've been waiting her for ages.M: Which train, madam?W: The 8:18 to Baker Street.M: The 8:187 I'm afraid you've made a mistake, madam.W: A mistake? My timetable says: Baker Street train—8:18.M: Oh, no, madam. The Baker Street train leaves at 8: 08.W: At 8:08?M: You see, madam. They changed the timetable at the end of April.W: Changed it? May I see the new timetable? What does it say?M: It says: Baker Street train—8:08.W: Hm! So the train isn't late. I'm late.(13)A．Because the train was late.B．Because the train was canceled.C．Because she didn't know the timetable was changed.D．Because she was late.

单项选择题物品x的需求方程估计为：Qx=10-2Px+4I-Py，式中，I为人均收入，Py为另一物品的价格。这一方程说明： A．物品x是正常货，物品x和y不相关 B．物品x是低档货，物品x和y为互补品 C．物品x为正常货；物品x与y为互补品 D．物品x为正常货；物品x与y为替代品