Although the causes of cancer ________, we do not yet have any practical way to prevent it．
#103264
A
have uncovered
B
have been uncovering
C
are uncovering
D
are being uncovered
推荐题目
_________ where the sound lab _________?
#103503
A
Has it decided; will built
B
Is it decided; it built
C
Has it been decided; will be built
D
Will it be decided; will be built
A great number of reporters _________ to London to report the 30th Olympic Games.
#102839
A
is invited
B
are invited
C
will invite
D
will be invited
----I’m sorry, but there is no smoking on this flight.----Oh, I _____ that. Sorry, I won’t again.
#104849
A
don’t know
B
didn’t know
C
won’t know
D
haven’t known
He will stop showing off, if no notice ＿＿ of him.
#104433
A
is taken
B
will be taken
C
takes
D
has taken
I haven' t seen Mary these past few days. I m afraid she ____ herself for some time.
#104846
A
isn't feeling
B
hasn' t been feeling
C
hadn't been feeling
D
wasn't feeling