I don't have to introduce him to you —— you know the boy .A) until .B) unless.C) since D) so理由：

I don't have to introduce him to you —— you know the boy .A) until .B) unless.C) since D) so理由：
I don't have to introduce him to you —— you know the boy .
A) until .B) unless.C) since D) so
理由：

I don't have to introduce him to you —— you know the boy .A) until .B) unless.C) since D) so理由：
C 既然
（ A 直到, B 除非,C所以,与句意都不符）