【正确答案】 A

【答案解析】[听力原文] Individual economic units can interact with one another in various ways. Three basic ways might be described as the market system, the administered system, and the traditional system. In a market system, individual economic units are free to interact among each other in the marketplace. It is possible to buy goods from other economic units or sell goods to them. In a market, transactions might take place through barter or money exchange. In a barter economy, real commodities are traded against each other. Apparently, finding someone who wants to trade my old car in exchange for a sailboat might not be an easy task. Thus, the introduction of money as a medium of exchange transactions considerably. In the modem market economy, commodities and services are bought or sold for money. An alternative to the market system is administrative control by certain agency over all transactions. This agency would issue commands or edicts as to how much of each commodity and service should be produced, exchanged, and consumed by each economic unit. Central planning might be one way of administering such an economy. The central plan shows the amounts of each good produced by the various companies and allocated to different households for consumption. This is an example of the complete planning of production, consumption, and exchange for the whole economy. In a traditional society, production and consumption patterns are controlled by tradition. Every person's place within the economic system is fixed by religion, parentage and custom. Transactions take place on the basis of tradition as well. People belonging to a certain group or caste might have an obligation to provide others with food, shelter and care for their health. Obviously, in a system where every decision is made on the basis of tradition alone, progress might be difficult to achieve. A stagnant society might result.