关于从句与分词的困惑

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

请教大家为什麽选D不选E？ THANKS

E的时态有问题, in the last year说明应该用一般过去时，他用了现在完成时态，没有道理

如果没有明显的标志（比如since）或者没有明显的理由使用 不用一般过去时

一般情况下 如果没有明显的错误 答案的时态要和题目中保持一致 不然就有改变句子原意的嫌疑

有道理,时态好象是有点问题,谢谢!