单项选择题

　　Economics can render service in the area of exchange, but its tools find less purpose when applied to paradigms dominated by alternative models of transactions and social relationships. In small groups gift-giving is substituted Line for the role of exchange, which entails obligation: people receiving gifts are expected to reciprocate in the future and this reciprocity binds small groups together, whereas exchange rarely does so. Two people exchange only when both benefit, neither incurring a social obligation as a result, and where social obligations exist, exchange may not work well. Exchange nevertheless allows for extremely complex interactions among strangers: when employing a product, a consumer benefits from the efforts of hundreds of anonymous people who have contributed to that commodity. Such analysis also has its limits in the case of an area such as government, for economics seeks regularities in social life, which are more likely to occur when no one individual has an appreciable effect on the group.

Which of the following might serve as the most appropriate title for the passage（）