除了下面A2,A3中所示各種型別外,這兩種從句均可由as或because來引導。但是用as引導原因從句較為穩妥;用because引導結果/原因從句較為穩妥(參見B)。
A 原因從句
1 由as/because/since 引導的原因從句:
We camped there as/because/since it was too dark to go on.
我們在那裡露宿是因為天太黑,不能再繼續往前走了。
As/Because/Since it was too dark to go on,we camped there.
因為天太黑不能再繼續往前走,我們就在那兒露宿了。
2 in view of the fact that可用as/since/seeing that來表示,但不能用because:
As/Since/Seeing that you are here,you may as well give me a hand.
既然你在這兒,你就幫我個忙吧。
As/Since/Seeing that Tom knows French,hed better do the talking.
3 在as/since/seeing that意指以前共知的'或共知的陳述時,可用if來代替:
As/Since/Seeing that/If you dont like Bill,why did you invite him?
既然/如果你不喜歡比爾,你為什麼邀請了他?
注意:if so的用法:
I hope Bill wont come.