老师你好！关于as,since,for,because 区别，我仔细看了辨析词典，成人高考教材都有介绍，但是我觉得这几个词区别不是很大，出题人不应该出这种题目。这种题目：

1. ____ everthing has been settled，I have nothing further to say. 

A. As  B.Because  C.Since  D.For 

在空白处填入适当的从属连词 

2.Jack was worried____he hadn’ t had any letter from his mother for long. 

3.We can’t go to see him today____we are going away very soon. 

4.He didn’t agree to join them,____he didn’t have time for a holiday.