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

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

 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

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

 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

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

I won't tell the student the answer to the math problem until he ________ on it for more than an hour．

1. A.
   has been working
2. B.
   will have worked
3. C.
   will have been working
4. D.
   isn't working

I won’t tell the student the answer to the math problem until he      on it for more than an hour

1. A.
   has been working
2. B.
   will have worked
3. C.
   will have been working
4. D.
   had worked