Questions 37 to 40 are based on the following passage：

　　Security and commodity exchanges are trading posts where people meet who wish to buy or sell. The exchanges themselves do no trading;they merely provide a place where prospective buyers and sellers can meet and conduct their business.

　　Wall Street， although the best known， is not the only home of exchanges in the United States. There are cotton exchanges in New Orleans and Chicago; the Mercantile Exchange， which deals in many farm products， in Chicago; and grain exchanges in many of the large cities of the Midwest. home exchanges， like the Chicago Board of Trade， provide market services for several kinds of products. These tradingposts where products may be bought or sold are called commodity exchanges.

　　The security exchanges， on the other hand, are meeting places where stocks and bonds are traded. Like the commodity exchanges ， they help serve the economic life of t he country. But when their operations get out of hand， they may become very dangerous.In l929， the security exchanges，or stock market， contributed to a crash a sudden， sharp decline in the value of securities. Many people lost fortunes;many corporations were bankrupted; many workers lost their jobs. The Crash of l929 has been attributed to many causes， among them wild and unwise speculation by many people and dishonest practices on the part of some businessmen and of some members of the exchanges.

　　Today，however，investing through security exchanges and trading on commodity exchanges has been made safer by regulations set up by the exchanges themselves and by regulations of the United States government， In l922，the government instituted the Commodity Exchange Commission which operated through the Department of Agriculture; and in l934，the Securities and Exchanges Commission， to protect investors and the public against dishonest practices on the exchanges.

　　37.Security and commodity exchanges are meeting places for buyers and sellers of__________.

　　A. stocks B. grain C. securities D. all of these

　　38. Among the reasons for the Crash of 1929 were__________.

　　A. unwise speculation by many people

　　B. dishonest practices by some businessmen

　　C. strict regulations of the Commodity Exchange Commission

　　D. both A and B

　　39.1nvestinR in securities has been made safer by__________.

　　A. the Securities and Exchange Commission

　　B. the Commodity Exchange Commission

　　C. Chicago Board of Trade

　　D. Chicago Mercantile Exchange

　　40.Implies but not stated :______________.

　　A. Some exchanges provide market services for several kinds of products

　　B. The role of the government has been an important factor in curbing dishonest practices on the exchanges

　　C. Investing in securities is unwise

　　D. Buying and selling securities is dishonest

21.D 22.B 23.C 24.A 25.D 26.A 27.B 28.A 29.D 30.C 31.B 32.A 33.B 34.C 35.D 36.B 37.D 38.D 39.A 40.B