关于og的一道阅读题

wangdaboyUID??3175433

A ten-year comparison between the United States and the Soviet Union in terms of crop yields per acre revealed that when only planted acreage is compared, Soviet yields were equal to 68 percent of United States yields. When total agricultural acreage (planted acreage plus fallow acreage) is compared, however, Soviet yield was 114 percent of United States yield.
　　From the information above, which of the following can be most reliably inferred about United States and Soviet agriculture during the ten-year period?
　　A. A higher percentage of total agricultural acreage was fallow in the United States than in the Soviet Union.
　　B. The United States had more fallow acreage than planted acreage.
　　C. Fewer total acres of available agricultural land were fallow in the Soviet Union than in the United States.
　　D. The Soviet Union had more planted acreage than fallow acreage.
　　E. The Soviet Union produced a greater volume of crops than the United States produced.
　　Explanation
　　If crop yield per planted acre was less in the Soviet Union than it was in the United States, yet crop yield per total (planted plus fallow) agricultural acreage was greater in the Soviet Union than it was in the United States, the percentage of the total acreage that was left fallow must have been lower in the Soviet Union than in the United States. Therefore, Choice A is the correct answer. Since the information provided in the paragraph
　　is given in terms of yield per acre, no conclusion can be drawn about actual acreage, so Choices B, C, and D are all incorrect. Similarly, it is impossible to determine the total volume of crops produced in the Soviet Union, so Choice E is incorrect.

wangdaboyUID??3175433

A选项该怎么解释啊

mikehitUID??3046487

休耕地占所有耕地（休耕地和种植地总和）的比例，美国的比苏联的高。
下面是推导过程：
X表示苏联粮食总产量 A表示苏联计划种植面积 A'表示苏联FALLOW ACREAGE
Y表示美国粮食总产量B表示美国计划种植面积 B‘表示美国FALLOW ACREAGE
条件是：1：X/A=0.68Y/B         2：X/(A+A')=1.14Y/(B+B')      
所以A/B>(A+A')/(B+B')
(B+B')/B>(A+A')/A
1+B'/B>1+A'/A
B'/B>A'/A
B/B'<A/A'
1+B/B'<1+A/A'
(B+B')/B‘<(A+A')/A'
结论  就是美国的休耕地比例B'/(B+B')大于苏联的A'/(A+A')

wangdaboyUID??3175433

3# mikehit 谢谢了~