Every possible means ________ to prevent the air pollution，but the sky is still not very clear.
#85546
A
were using
B
have used
C
has been used
D
was used
推荐题目
He is the only one of the people here who ____ how to operate the computer.
#85796
A
knows
B
know
C
had known
D
known
The number of people visiting the exhibition ______ 50, and a number of them ____ painters.
#85600
A
was; was
B
were; was
C
was; were
D
were; were
Either you or he _________ to be invited to the party．
#85883
A
is likely
B
are likely
C
is possibly
D
are possibly