I won’t tell the student the answer to the math problem until he ___ on it for more than an hour.
A.has been working B.will have worked C.will have been working D.had worked正确答案A
I won’t tell the student the answer to the math problem until he ___ on it for more than an hour.
A.has been working B.will have worked C.will have been working D.had worked正确答案A