都選for
原因狀語從句
一 because,since,as和for引導(dǎo)的原因狀語從句
1 because(因為）：表示直接的原因或理由,著重點在從句,用于回答why,語氣最強.
He didn't go to school because he was ill.
Why didn't he go to school?Because he was ill.
2 since(既然）：一般表示對方已知的,無須加以說明的即成事實的理由,全句中心在主句,語氣比
because弱.
Since you are ill,I'll go alone.
3 as(由于）：表示十分明顯的原因,一般說明因果關(guān)系,著重點在主句,語氣較弱.
As it is snowing,we shall not go to the park.
4 for(因為,其理由是）：是個并列連詞,只能放在另一個并列句后面,表示推理或解釋,或用作附加說明,表示新的情況,而不是指理由或原因,語氣最弱,一般不放在句首.
The day breaks,for the birds are singing.
* for表示因果關(guān)系時,可以同because交替使用,但for前須用逗號,而because則不必.
You couldn't have seen him because he wasn't there.
= You couldn't have seen him,for he wasn't there.
*當(dāng)原因是顯而易見的或已為人們所知,就用as或since,且多放在句首.
Since/ As the weather is so bad,we have to delay our journey.
二 now (that) (既然,現(xiàn)已...所以,當(dāng)...才）；
Now (that) you've grown up,you should not behave like a child.
Now (that) I am older I see things differently.
Now (that) I have heard the music I understand why you like it.
這兩個題我也不會,高考這種題考的不多吧,我們上高三的時候,很少考for的這種用法.如果不明白的話,就把它記住吧.