[讨论]GWD9-3

jomn111

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
    

一个疑问：D中的 plummet是过去完成的动作，为什么能用ing形式？

feifeizoe

D中的plummet应该是过去式吧

cdinitialb

D中应为PLUMMET应该是过去时（in the last year）

D选项前面的结构是独立主格，表达原因。独立主格中的动词如果是主动形式要用现在分词形式