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
—Why didn’t you buy the gold ring? —I ______ but I didn’t have the money.
#103211
A
would have
B
bought
C
would like to
D
had bought
---What ‘s the matter with you? --- You _____ my heart. - -- But I didn’t mean to hurt you.
#102840
A
broke
B
are breaking
C
had broken
D
have broken
—Hi , Tracy , you look tired. —I’m tried. I ______ the living room all day.
#102468
A
painted
B
had painted
C
have been painting
D
have painted
By the end of the last month, I_________all the CDs Of Justin Bieber.
#102399
A
collect
B
collected
C
have collected
D
had collected
These days, we _____ for our final exams.
#102111
A
are prepared
B
have prepared
C
are preparing
D
will prepare