这些是什么（）

A.What's that

B.What color is it

C.What are these

What is the author's attitude towards the eating habits in Brazil？

A．The author doesn't think much of them.

B．The author likes those in the U. S. better.

C．The author appreciates them very much.

D．The author shows no emotions whatever.

What is the 'biggest city in the world？ That is, (21) city has the largest population？ This seems like (22) question to answer, but actually it isn't.

It's actually rather difficult to say which cities (23) the largest. There are two reasons for this difficulty. First of all, it isn't easy to determine a city's boundaries, that is, where a city ends. Nowadays, nearly all cities have a large (24) area around them. So when we talk about the population of a city, we often mean the population of the whole metropolitan area around the city. That means that it's difficult to determine what the population of a city is because it's difficult to define what a city is.

The second reason that it is difficult to 25 the population of different cities is this: it is almost impossible to get (26) about the population of all cities for the same year. For example, we might get an estimate of New York's population in 1979 and an (27) of Mexico City's population in 1981. So we real ly can't compare the numbers because the information is for (28) different years. And the population of cities changes rather quickly, especially in some cases. For example, the population of Jakarta, Indonesia, may increase by 5% each year, so the population figure will change rather quickly.

So we can say that these are our two (29) for comparing the populations of cities: one, it's difficult to determine the (30) of a city, and two, it is difficult to get accurate information.

21. A. what

B. which

C. where

D. how

A.What are those

B.What is this

C.What are these

A.What's your hobby

B.My hobby is making models

C.What do you like doing

A.What’s that

B.What are they

C.What colour

下表显示了一个以常数边际成本10美元生产的垄断者面临的需求曲线。

(1)计算该厂商的边际收益曲线。

(2)该厂商的利润最大化产量和价格是多少？该厂商的利润为多少？

(3)在一竞争性行业中均衡价格和数量各为多少？

(4)如果该垄断者被迫以完全竞争的均衡价格生产，社会得益是什么？结果是谁获益谁受损？

The following table shows the demand curve facing a monopolist who produces at a constant marginal cost of $ 10.

a. Calculate the firm' s marginal revenue curve.

b. What are the firm's profit - maximizing output and price？ What is its profit？

c. What would the equilibrium price and quantity be in a competitive industry？

d. What would the social gain be if this monopolist were forced to produce and price at the competitive equilibrium？ Who would gain and lose as a result？

提示：Joe和Henry谈起报上的一篇文章，Henry问什么报，什么文章。他没用读完这篇文章，但标识下午要读，然后告别。

Joe ：Hi， have you read today‘s newspaper？

Henry：_________1___________？

Joe ：The People‘s Daily.

Henry：________2__________. But I only looked through it while having lunch.

Joe ：Did you notice an interesting article？

Henry：___________3___________？

Joe ：About air pollution.

Henry：________4__________. On which page？

Joe ：On page 5. At the bottom.

Henry：Good. I‘ll read it this afternoon.

Joe ：Don‘t forget to tell me what you think after reading it.

Henry：Sure. __________5__________.

Joe ：See you.

A.is it

B.it is

C.it are

A.()

B.simple sentence

C.compound sentence

D.complex sentence

E.compound-complex sentence

A.No, it's a parrot

B.This is a parrot

C.It's a parrot