I won’t tell the student the answer to the math problem until he ______ on it for more than an hour. 
#104700
A
has been working
B
will have worked
C
will have been working
D
had worked
推荐题目
      ---____ the paper ?--- No, I have still got one page to finish.
#103668
A
Have you done
B
Do you do
C
Did you do
D
Had you done
The theory he had stuck _______ to be true.
#104225
A
proved
B
to proving
C
to prove
D
to proved