题目内容
（请给出正确答案）
They ______ us since five o'clock this morning until now.
A．are helping
B．help
C．have helped
D．have been helping
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They ____ us since five o’clock this morning.
A、are helping
B、have been helping
C、was helped
D、has been helping
A.It has
B.There has
C.It is
D.There is
Visitors from the US have increased______8 percent since last year.
A．in
B．by
C．with
D．from
A. during
B. in
C. for
D. since
A.for
B.in
C.since
D.during
Since our knowledge is ______, none of us can exclude the possibility of being wrong.
A．delicate
B．restrained
C．controlled
D．finite
No one sells organs in the US since it is illegal.
A．Right
B．Wrong
C．Not mentioned
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