关于介词并列连词

在英语中，状语从句放在主句前后均可，区别在于：状语从句放在句首时要用逗号分开，状语从句放在句尾时不需逗号。因为英语习惯上是把主句置于首，后接其他部分，状语从句只是一个句子的连带部分，一般放在后面。但是为了强调，就把强调的部分放到句首，用逗号分开。
如下面的句子：
He often helps me with my English although he is quite busy。
Although he is quite busy, he often helps me with my English.
He was not at home when I went to see him.
When I went to see him, he was not at home.
望对你有帮助。