单选题：Directions : There are 2 passages in this section. Each pass

Directions : There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four Choices marked A．, E B．, E C．and D J . You should decide on the best choice and mark the corresponding letter oh Answer Sheet 2 with a single line through the centre.
Questions are based on the following passage.
　　The United States is said to have a mixed economy because privately Owned business and government both play important roles. Indeed, some of the most enduring debates of American economic history focus on the relative roles of the public and private sectors.
　　The American free enterprise system emphasizes private ownership. Private businesses produce most goods and services, and almost two-thirds of the nation's total economic output goes to individuals for personal use (the remaining one-third is bought by government and business). The consumer role is so great, in fact, that the nation is sometimes characterized as having a "consumer economy".
　　This emphasis on private ownership arises, in part, froth American beliefs about personal freedom. From the time the nation was created, Americans have feared excessive government power, and they have sought to limit government's authority over individuals -- including its role in the economic realm. In addition, Americans generally believe that an economy characterized by private owner- ship is likely to operate more efficiently than one with substantial government ownership.
　　When economic forces are unfettered, Americans believe, supply and demand determine the prices of goods and services. Prices, in turn, tell businesses what to produce; if people want more of particular goods than the economy is producing, the price of the goods rises. That catches the attention of new or other companies that, sensing an opportunity to earn profits, start producing more of that goods. On the other hand, if people want less of the goods, prices fall and less competitive producers either go out of business or start producing different goods.
　　There are limits to free enterprise, however. Americans have always believed that some services are better performed by public rather than private enterprise. For instance, in the United States, government is primarily responsible for the administration of justice, education, the road system, and national defense.
　　In this mixed economy, individuals Can help guide the economy not only through the choices they make as consumers but through the votes they cast for officials who Shape' economic policy. In recent years, consumers have voiced concerns about product safety, environmental threats posed by certain industrial practices, and potential health risks citizens may face; government has responded by creating agencies to protect consumer interests and promote the general public welfare.
According to the passage, the U. S. is sometimes called