[求助]疑惑一题 关于While的疑问

tianwan

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

The key is E. Why not D?

tianwan

I think "while" plus "has" is not a grammatic usage. Can "while" match perfect tense?

tianwan

我怎么看不出转折的意思呀？

tianwan

如果不是转折，while不能和has连用。

tianwan

when sb/sth has可以，while sb/sth has不行。while只能表示同时的。我看，关键还是这一句里while有没有让步。

tianwan

bingo！多谢NN们。

tianwan

in the last year可以和has plummeted连用，during/in the last/past year应该都可以和完成时连用。

你用“the last”在大全搜索，就可以看到很多例子。

从语法上讲D和E都可以，但问题是D没有转折含义。所以E更好。

tianwan

应该是现在完成时和一般过去时应该都可以连用in the last year。不过现在完成时表示和现在有联系，一般过去时表示和现在无联系。

关于完成时和一般过去时的区别，你最好查一本语法书，因为我们讨论的只是一个局部，不看语法书，就无法建立全面的认识，会有无穷多的新问题出现。

比如，这一题我们讨论的是现在完成时可不可以和in the last year连用，结论是可以。但我并没有说一般过去时不可以连用in the last year。至于past和last在语法书上，在讲述关于现在完成时的时候，就是in the past（last）few year。