[简答题]Translate the following passages into Chinese.        Economic activities began with the caveman, who was economically self-sufficient. As the primitive population grew and developed, the principle of division of labour evolved. One person was more able to perform some activity than another, and therefore each person concentrated on what he did best. While one hunted, another fished. The hunter then traded his surplus to the fisherman, and thus each benefited from the exchange. That was how trade first began.        International trade is the exchange of goods between nations. It took place for many reasons. Countries that lack some resources within their own boundaries must buy from countries that export them. Second, a country often does not have enough of a particular item to meet its needs and has to import some to satisfy its requirement. Third, one nation can sell some items at a lower cost than other countries and will also buy what it needs from those countries that have a comparative advantage in the desired items. Finally, even though a country can produce enough of an item at reasonable costs to meet its own demand, it may still import some from other countries for innovation or variety of style.