I don’t have to introduce him to you you know the boy..A. until B. unlessC. sinceD. but

问题补充：

I don’t have to introduce him to you you know the boy..

A. until

B. unless

C. since

D. but

答案：

A. until

B. unless

(答案→)C. since

D. but

解析：当从句中有since+一般过去时，主句用现在完成时，故选C