7.Although the causes of cancer ____， we do not yet have any practical way to prevent it.
#105343
A
are being uncovered
B
have been uncovering
C
are uncovering
D
have uncovered
推荐题目
“The moment ________ soon”，he thought to himself，waiting nervously.(2012·湖南)
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A
came
B
has come
C
was coming
D
is coming
The College Entrance Examination________near, so you should be prepared for it.
#105333
A
is drawing
B
draws
C
drew
D
has drawn
Britain is being ________ in the race for new markets.
#105311
A
left alone
B
left out
C
left behind
D
left over
— Why do you do volunteer work in the North-West?— I_______ to improve the lives of the children there through my efforts.
#105303
A
was trying
B
have tried
C
am trying
D
tried
I'll go to the library as soon as I finish what I ________.
#105315
A
was doing
B
am doing
C
have done
D
had been doing