单选题 There are various ways in which individual economic units can interact with one another. Three basic ways may be described as the market system, the administered system, and the traditional system. In a market system, individual economic units are free to interact each other in the marketplace. It is possible to buy commodities form other economic units or sell commodities to them. In a market, transactions may take place via barter or money exchange. In a barter economy, real goods such as automobiles, shoes, and pizzas are traded against each other. Obviously, finding somebody who wants to trade my old car in exchange for sailboat may not always be an easy task. Hence the introduction of money as a medium of exchange eases transactions considerably. In the modern market economy, goods and services are bought or sold for money. An alternative to the market system is administrative control by some agency over all transactions. This agency will issue edicts or commands as how much of each good and service should be produced, exchanged, and consumed by each economy unit. Central planning may be one way of administrating such an economy. The central plan, drawn up by the government, shows the amounts of each commodity produced by the various firms and allocated to different households for consumption. This is an example of complete planning of production consumption, and exchange for the whole economy. In a traditional society, production and consumption patterns are governed by tradition: every person's place within the economic system is fixed by parentage, religion, and custom. Transactions take place on the basis of tradition too. People belonging to a certain group or caste may have an obligation to cater for other persons, provide them with food and shelter, care for their health, and provide for their education. Clearly, in a system where every decision is made on basis of tradition alone, progress may be difficult to achieve. A stagnant society may result.

单选题 The word "real" in "real goods" in the second paragraph could best replaced by ______.

单选题 According to the passage, a barter economy can lead to ______.

单选题 According to passage, ______ has the greatest control in an administered system.

单选题 Which of the following is NOT mentioned by the author as a criterion for deciding a person's position in a traditional society?

单选题 What is the main purpose of the passage?

单选题 In the market system, money acts as a role of______.

单选题 The old system is based on ______.