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
(5) 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
(10) 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 best describes the organization of the passage（）