I thought I would get a really good mark but I got an E.
I thought I would get a really good mark, but I got an E.
上下两句中用逗号和不用有什么区别?什么情况下我们用下句而不用上句?
如果 but 后面接一个句子, but 的前面用与不用逗号没有什么区别。