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
—Do you know if the foottball game has started yet?—Started? It must be certain who ________ by now.
#104474
A
is winning
B
wins
C
has won
D
would win
The battle lasted for a few hours and at last the enemy ________.
#103830
A
was defeated
B
were beat
C
were won
D
defeated
–Hi, Tom, You look tired. --Yes, I _____________ the room all the afternoon.
#102380
A
painted
B
had painted
C
have painted
D
have been painting
—Wow, what a large crowd!—Yes, And they______ in the cold wind for hours. You know, Premiere Wen Jiabao is coming here.
#103751
A
will be waiting
B
have waited
C
are waiting
D
have been waiting