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It is necessary _____ something to protect our environment.
#50188
A
do
B
to do
C
does
D
doing
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The problem is         difficult for me        work out.
#51005
A
very; to
B
enough; to
C
so; that
D
too; to
The young mother kept ______ the house with three children in it , because she wanted to keep it ______.
#48871
A
cleaning; clean
B
cleaning; cleaning
C
clean; clean
D
clean; cleaning
Teachers’ job is ______ the students learn well.
#50176
A
helping
B
help
C
to help
D
helped
He is very serious. No one can make him___.
#50906
A
laugh
B
laughs
C
to laugh
D
laughing
He is too tired _______any longer.
#49889
A
not to walk
B
to walk
C
walking
D
not walking