[求助]prep 2-175 请进

        175.  (30931-!-item-!-188;#058&005850)  (GWD-9-Q3)

Because of wireless service costs plummeting in the last year, and as mobile phones are increasingly common, many people now using their mobile phones to make calls across a wide region at night and on weekends, when numerous wireless companies provide unlimited airtime for a relatively small monthly fee.

A. Because of wireless service costs plummeting in the last year, and as mobile phones are increasingly common, many people

B. As the cost of wireless service plummeted in the last year and as mobile phones became increasingly common, many people

C. In the last year, with the cost of wireless service plummeting, and mobile phones have become increasingly common, there are many people

D. With the cost of wireless service plummeting in the last year and mobile phones becoming increasingly common, many people are

E. While the cost of wireless service has plummeted in the last year and mobile phones are increasingly common, many people are

是简洁性么？

我选择的是E，答案为D，我实在觉得E挺好的，是因为简洁性，才去掉的么

很好的资源，谢谢你，平行结构+with/which的用法，似乎明白了，在好好琢磨下～～非常感谢

总结一下我对while的理解：

while 放在句首表示对比，有although 的意思. 两句话主语不用对应，但是意思上一定是相反的。例如ＯＧ12-60

while all states face similar industrial waste probelms, the predominant industries and the regulatory enviornement of each state obviously determint the types and amounts of waste produced, as well as the cost of diposal. 

放在句中是但是，让步的意思。但是不如but 好，（记不得是OG那个版本上说的了，while可以代表多个意思，如当...，不如but明确）。

就本句话的结构上说，while从句中的and两边都应该是，has done的时态。 这是老头们经常的考点。

D, 是独立主格作状语.with 引导的不受时态，数的限制。 要说简洁的话，还是D要简洁，看得比较清楚，不用让读者去想倒地是当，还是虽然。

in the last year这个时间状语可以做have plummeted这个现在完成时的时态的时间状语吗?

可以用这一点排除E吗?

这个要看语义把，楼上都说的对... 主要是时态的问题...