关于破折号的使用

A recent poll indicates that many people in the United States hold a combination of conservative and liberal political views; i.e, they denounce bid government, saying government is doing too much and has become too powerful, while at the same time supporting many specific government programs for health car, education, and environment.

A.they denounce bid government, saying government is doing too much and has become too powerful, while at the same time supporting

B. they denounce big government--they say that government is doing too much and has become too powerful--but supporting at the same time

C.they denounce big government, they say that government is doing too much and it has become too powerful, while they support at the same time

D.while they denounce big government, saying that government is doing too much and has become too powerful, at the same time supporting

E.while they are denouncing big government--they say that government is doing too much and it has become too powerful--supporting at the same time

主要想请教一下B和E中关于破折号的用法，破折号前后如果是句子，句子成分都必须是完整的吗？谢谢

刚才翻了下牛津词典，是这么说的

dash 破折号

1、in formal English, instead of a colon or semicolon, to indicate that what follows is a summary or conclusion of what has gone before

You've admitted that you lied to me — how can I trust you again?

2、singly or in pairs to separate a comment or an afterthought from the rest of the sentence

He knew nothing at all about it — or so he said. 

第一种情况说了是在非正式英语中,破折号后面作为结论。

所以大多数例子都是前面是句子，破折号后面是对前句的评语或者补充。

还是要根据具体题目吧，如果其他选项有明显错误，那只能选破折号表示结论了。

总之两种用法都是对的。只不过前后都有成分的随便罢了。