课后练习：

1. There are several reasons international trade exists.

A. why B.because C. that D. which

2. Some nations possess natural deposits their own requirements other nations have none.

A. atexcess of; while B. inexcess of; and

C. inextenceof; that D. inexcess of; while

3. With thedevelopment of manufacturing and technology, there

another incentive fornations to exchange their products.

A. arose B. rose C.arise D. rise

4. The theory ofcomparative advantage, also called the comparative cost theory, David Ricardo and other economistsin the nineteenth century.

A. is developed by B. was developed by

C. was developed D. are developed by

5. there areminorrelative differencesin theefficiencyof producing a commodityeven the poor country can have a comparative advantagein producing it.

A. As long as B. As short as C. As soon as

6. This principleis the of specialization into trades andoccupations.

A. base B. basis C. basic D.basses

7. Goods and rawmaterials around the world.

A. have to transpose B. have to be transposed

C. have to aretransposed

(不定式被动语态：to be done)

8. Thus, insurance isanother service some nations specialize.

A. in which B. that C. when D. ofwhich

9. Invisible tradecan be as important to some nations the export of raw materials or commodities isto others.

A. as B. than C. so D.to

现在以“中文形式”出几道“理阅读解”题——

1、“穷国在生产上没有比较优势”，这句话正确吗？

错误。即使是穷国在生产上也会有比较优势。

2、国家之间货物自由流通的另一个障碍是什么？

另一个障碍是：人为的贸易壁垒。例如关税和配额。

3、文中提及的无形贸易有几种？分别是什么？

3种，包括运输服务、保险服务和旅游服务。

4、……你也来为自己出道题吧！