but作为连词连接两个句子时,前面为什么都有逗号?有没有资料为证?

谢谢,告诉我我会加分!
but
KK: []
DJ: []
conj.
1. 但是
It is hot in summer here, but it is not cold in winter.
这里夏天热,但冬天不冷。

类似这样的句子。

第1个回答  2009-01-27
but是连词,没有这种用法啊,但是however可以这么用,作为一个插入语
第2个回答  2009-02-08
but表示转折,在这之前必须有与之相反的语句才可以运用本回答被提问者采纳
第3个回答  2009-01-27
谁说都有逗号呀?
You use but to introduce something which contrasts with what you have just said, or to introduce something which adds to what you have just said.
`You said you'd stay till tomorrow.'—`I know, Bel, but I think I would rather go back.'...
Place the saucepan over moderate heat until the cider is very hot but not boiling...
He not only wants to be taken seriously as a musician, but as a poet too.

参考资料:collins字典第5版

第4个回答  2020-03-20
我遇见过这样的句子:Mary went tothe books office ,but all the tickets has been booked这个是有时有,有时又没有这时候but其实是一个连词,相当于and那样,但but是转折,连接的是两个句子
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