请问托福00-08阅读题23

I2109UID: 2139053

23. According to the passage, why was the Civil War a stimulus for mechanization?
(A) The army needed more grain in order to
    feed the soldiers.
(B) Technology developed for the war could
   also the used by farmers.
(C) It was hoped that harvesting more grain
   would lower the price of grain.
(D) Machines were needed to replace a
   disappearing labor force.
答案是B，我怎么想都不通（我选的是D），如果有做完此题并有时间回复的同学愿意帮忙的话我十分感谢！

阅读原文如下：

During the second half of the nineteenth century, the production of food and feed crops  
in the United States rose at an extraordinarily rapid rate.Com production increased by four  
and a half times, hay by five times, oats and wheat by seven times. The most crucial factor
Line   behind this phenomenal upsurge in productivity was the widespread adoption of
(5)    labor-saving machinery by northern farmers. By 1850 horse-drawn reaping machines that
cut grain were being introduced into the major grain-growing regions of the country.
Horse-powered threshing machines to separate the seeds from the plants were already in
general use. However, it was the onset of the Civil War in 1861 that provided the great  
stimulus for the mechanization of northern agriculture. With much of the labor force
(10)    inducted into the army and with grain prices on the rise, northern farmers rushed to avail
themselves of the new labor-saving equipment[/u]. In 1860 there were approximately 80,000
reapers in the country; five years later there were 350,000.
        After the close of the war in 1865, machinery became ever more important in northern
agriculture, and improved equipment was continually introduced. By 1880 a self-binding
(15)      reaper had been perfected that not only cut the grain, but also gathered the stalks and
bound them with twine. Threshing machines were also being improved and enlarged, and
after 1870 they were increasingly powered by steam engines rather than by horses. Since
steam-powered threshing machines were costly items-running from $ 1,000 to $4,000
-they were usually owned by custom thresher owners who then worked their way from
(20)    farm to farm during the harvest season. “Combines” were also coming into use on the
great wheat ranches in California and the Pacific Northwest. These ponderous machines
       —sometimes pulled by as many as 40 horses – reaped the grain, threshed it, and bagged
       it, all in one simultaneous operation.
             The adoption of labor-saving machinery had a profound effect upon the sale of
(25)    agricultural operations in the northern states-allowing farmers to increase vastly
their crop acreage. By the end of century, a farmer employing the new machinery
could plant and harvest two and half times as much corn as a farmer had using hand
methods 50 years before.

victoriapczUID: 2117546

正确答案是选D 你的参考答案错了

I2109UID: 2139053

问了好些人大部分说正确答案就是D，是我的答案错了，谢谢！