it指代问题

包子不包子

求教~~ 大牛~~

For about fourcents an acre the UnitedStates acquired, in the Louisiana Purchase of 1803,

828,000 squaremiles, more than doubling the country's size and it brought its western border within reach of the Pacific Ocean.

and it brought在语法上应该与主句the United States acquired并列，it没有合理的指代对象

这是答案的解释 都并列了为什么it还是没有指代对象？
还有啊 如果在and it brought 的 and 之前加逗号 会产生什么影响么？

One automobile manufacturer has announced plans to increase the average fuelefficiency of its

sport utility vehicles by 25 percent overthe next five years,amounting to roughly five miles pergallon, and it would represent the first significant change in the fuelefficiency of any class of passenger vehicle in almost two decades.

It指代manufacture

两句话是类似的 怎么第二句就有指代了 ><
还有啊 amounting 的用法为什么错了 是逻辑错误麽 不能修饰主语 manufacture？

Spencer125

For about fourcents an acre the UnitedStates acquired,这是介词引导的句子，所以不能做主语。这句话没有谓语,所以错了.   之前加不加逗号,因为这个句子没有谓语,所以不影响了。
对于第二句话,  it 当然和前面的manufacturer并列．　amounting to 如果修饰manufacturer的话意思上行不通，因为题目意思要表示数量上达到多少，而不是manufacturer达到多少．

包子不包子

Spencer125 发表于 2013-7-11 09:53
For about fourcents an acre the UnitedStates acquired,这是介词引导的句子，所以不能做主语。这句话没有 ...

逻辑最强 恩恩
包子谢过~