【单选题】

Industrialization came to the United State after 1790 as NorthAmerican entrepreneurs　　　 increased productivity by reorganizing work and building factories. These innovations　　　 in manufacturing boosted output and living standards to an unprecedented extent; the　　　 average per capita wealth increased by nearly 1 percent per year―30 percent over(5) the course of a generation. Goods that had once been luxury items became part of　　　 everyday life.　　　 The impressive gain in output stemmed primarily from the way in which workers made　　　 goods, since the 1790’’s, NorthAmerican entrepreneurs―even without technological　　　 improvements―had broadened the scope of the outwork system that mace manufacturing(10)more efficient by distributing materials to a succession of workers who each performed a　　　 single step of the production process. For example, during the 1820’’s and 1830’’s the shoe　　　 industry greatly expanded the scale and extend of me outwork system. Tens of thousands　　　 of rural women, paid according to the amount they produced, fabricated the "uppers" of　　　 shoes, which were bound to the soles by wage-earning journeymen shoemakers in dozens(15)of massachusetts towns, whereas previously journeymen would have made the enure　　　 shoe. This system of production made the employer a powerful "shoe boss" and eroded　　　 workers’’ control over the pace and conditions of labor. However, it also dramatically　　　 increased the output of shoes while cutting their price.　　　 For tasks that were not suited to the outwork system, entrepreneurs created an even(20)more important new organization, the modem factory, which used power-driven machines　　　 and assembly-line techniques to turn out large quantities of well-made goods.As early　　　 as 1782 the prolificDelaware inventor OliverEvans had buiit a highly automated,　　　 laborsaving flour mill driven by water power. His machinery lifted the grain to the top of　　　 the mill, cleaned it as it fell into containers known as hoppers, ground the grain into flour,25)and then conveyed the flour back to the top of the mill to allow it to cool as it desended　　　 into barrels. Subsequently, manufacturers made use of new improved stationary steam　　　 engines to power their mills. This new technology enabled them to build factories in the　　　 nation’’s largest cities, taking advantage of urban concentrations of inexpensive labor,　　　 good transportation networks, and eager customers.What is the passage mainly about

A、The difficulties of industrialization in NorthAmerica
B．The influence of changes in manufacturing on the growth of urban centers
C．The rapid speed of industrialization in NorthAmerica
D．Improved ways of organizing the manufacturing of goods