1) for是并列连词,不能置于含两个并列分句的句子的句首,只能将其放在两个分句中间。
判断改错:(错) For he is ill, he is absent today.
(对) He is absent today, for he is ill.
2) so为连词, therefore一般为副词。例如:
He hurt his leg, so he couldn’t play in the game. 他的腿受伤了,不能上场。
I think; therefore I exist. 我思故我在。