单选题
·Read the article below about cost.
·Choose the best word to fill each gap, from A, B, C or D.
·For each question 19—33, mark one letter (A, B, C or D) on your Answer Sheet.
·There is an example at the beginning.

{{B}}Cost as a Factor in Supply{{/B}}
In a purely competitive market, the supplier of goods and services has no control over the market price, because he produces too little to influence market conditions. With no difference between his product and the products{{U}} (19) {{/U}}his competitors, he will sell nothing if he charges above the market price and he will sell all if he charges at or below the market price. However, in considering the price, be must take cost of production{{U}} (20) {{/U}}. There are times when he may be willing to sell below his cost. This might happen when prices tumble for{{U}} (21) {{/U}}a short time. However, no business person can{{U}} (22) {{/U}}lose money for a prolonged (延长的) period. He must{{U}} (23) {{/U}}of his costs in relation to the market price if he is to compete successfully and earn a profit.
Many people have the impression that{{U}} (24) {{/U}}production increases, costs per unit decrease. {{U}}(25) {{/U}}mass production has made this true in certain industries and at certain levels of production, {{U}}(26) {{/U}}logic and practical experience have shown that costs per unit begin to rise beyond a certain level of production. Some economists{{U}} (27) {{/U}}this principle as the law of increasing costs.
The reason why{{U}} (28) {{/U}}rise as production goes up is complex. However, it is easy to recognize that as production goes up, the need for additional factors of production will also grow, resulting{{U}} (29) {{/U}}competitive bidding (出价) in the marketplace for the factors of production. If a producer needs{{U}} (30) {{/U}}skilled labour to produce more, and none of this labour is unemployed, the producer will have to get{{U}} (31) {{/U}}from other sources. This can be done by{{U}} (32) {{/U}}higher wages. Higher bidding would also apply to the other factors of production. We must also recognize that not all labour is equally productive, {{U}}(33) {{/U}}not all land is equally fertile (肥沃的) and not all ore is equally rich in the mineral wanted.

【正确答案】 C

【答案解析】被选择项是插入成分，去掉这一成分句子在语法上仍然成立：This might happen when prices tumble for a short time．但作者强调的是，供应商这样认为，即，认为价格会在短时期内下跌。for是介词，它后面可以跟名词或名词从句，做它的宾语，不能直接跟句子，因此A和D不能选择。 what可以引导名词从句。例如：He is not interested in what you told him。他对你告诉他的事并不感兴趣。I did not do what you expected me to do．我没有做你希望我做的事。

【正确答案】 A

【答案解析】afford在这里的意思是：经得起(做某事，或发生某事)。这个句子的意思是：然而，没有哪个商人能经得起长时期的赔钱。例如：We couldn't afford to ignore the problem of pollution。我们可不能忽视污染的问题。affordable：(价格)付得起的，不贵的。例如：The store sells things which are very affordable．那家商店的东西不贵。afford to中的to不能省略，它引出动词不动式，所以D是错误的选择。但afford后可直接跟名词，意为；付得起(钱或时间)。例如：They couldn't afford the medical treatment．他们付不起治疗费。

【正确答案】 B

【答案解析】as在这里是“当……的时候”的意思。这句话是说：许多人认为，当生产增长时，单位成本便下降。while在做“当……”解释时，常常用于动词的进行时态，例如：She was reading while her broth er was playing guitar。虽然now that也是连接词，但它的意思是；既然。例如：Now that you have made some money, you can use it to do what you have always wanted to do。你已经赚了一些钱，那你就可以去做你一直想做的事了。

【正确答案】 D

【答案解析】根据上下文，以及该句的意思，这里需要一个引导让步状语从句的连接词，while在句中起此作用时，其意与although相同。这一状语从句的意思是：虽然大规模生产已在一些行业在某种程度证实了这一点……例如：While the light turned green，the traffic couldn't move a bit．虽然已是绿灯，车辆仍无法前行寸步。because和since引导原因状语从句，而when引导时间状语从句。