Although the causes of cancer_____, we do not yet have any practical way to prevent it.
#104936
A
are being uncovered
B
have been uncovering
C
are uncovering
D
have uncovered
推荐题目
(2013·山东，27)—Oh no! We're too late.The train________.— That's OK.We'll catch the next train to London.
#99732
A
was leaving
B
had left
C
has left
D
has been leaving
The weather forecast says there will be wind from the northwest tonight. That always _____ snow with it at the time of year.
#102077
A
brought
B
brings
C
will bring
D
has brought
He__________ he would be able to leave tomorrow, but it's beginning to took difficult．
#103718
A
hopes
B
was hoping
C
had hoped
D
hoped
The two boys_____ games on the computer for three hours, and they would continue till midnight
#104829
A
were playing
B
had played
C
had been playing
D
has been chatting
—Do you regret not having accepted their invitation?—Why should I? I as much, but I’m glad to devote myself to what interests me most.
#100662
A
didn’t earn
B
don’t earn
C
hadn’t earned
D
haven’t earned