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
The population of China___ to many times what it was in 1949, and most of its population ___ farmers.
#85694
A
have grown; are
B
have grown; is
C
has grown; is
D
has grown; are
A library together with 5000 books for the school.
#86091
A
was provided
B
were provided
C
provided
D
have provided
Mary three of her classmates invited to the party.
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A
as well; has been
B
and; have
C
as well as；was
D
as good as; were