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
—What’s the noise outside? —The kids ______ in the garden.
#100329
A
have played games
B
play games
C
are playing games
D
are played games
If city noises ______ from increasing, people______ shout to be heard even at the dinner table 20 years from now. (MET1992 ) 
#104333
A
are not kept; will have to
B
are not kept; have to
C
do not keep; will have to
D
do not keep; have to