You have failed two tests. You’d better start working harder you won’t pass the course.A

问题补充：

You have failed two tests. You’d better start working harder, you won’t pass the course.

A. and

B. or

C. but

D. so

答案：

A. and

(答案→)B. or

C. but

D. so

解析：考查连词。and 和，并且； or 否则，或者；but但是；so因此。句意：你已经两次考试不及格了。你最好开始努力学习，否则你不可能通过这门课程。故选B。