看了前人讨论，我还是不明白（1)B为何不对？（2）答案是E,但是好像很多觉得D,请指教！谢谢！

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.

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

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

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

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

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

in B, it is "many people now using...." definitely wrong.So only D &

E are left.

the tense in E seems too weird. So I pick D.

i chose D also.

"in the last year" should be conflicting against perfect tense. That why I give up E.

D中的with是有"因為"的意思

Longman dictionary:
14   because of a situation that exists:
With John away there's more room in the house.
with something doing something   
I can't do my homework with all this noise going on.

with...... 不是可以看成是独立主格结构么？

我觉得E的while有点改变原来语意