单选题 .  As suppliers of most of the food we eat and of raw materials for many of industrial processes, agriculture is clearly an important area of the economy. But the industrial performance of agriculture is even more important than this, or in nations where the productivity of farmers is low, most of the working population is needed to raise food and few people are available for production of investment goods or for other activities required for economic growth. Indeed, one of the factors related most closely to the per capital income (人均收入) of a nation is the fraction of its population engaged in farming. In the poorest nations of the world more than half of the population lives on farms. This compares sharply with less than 10 percent in Western Europe and less than 4 percent in the United States.
    In short, the course of economic development in general depends in a fundamental way on the performance of farmers. This performance, in turn, depends on how agriculture is organized and on the economic environment or market structure, within which it functions. In the following pages the performance of American agriculture is examined. It is appropriate to begin with a consideration of its market structure.1.  This passage is most probably ______.