单项选择题
Making energy use completely harmless to the environment（）very difficult and usually economically expensive.
A.are
B.is
C.have been
D.shall be
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The thief was so （）by teh bright lights and barking dogs that he left hastily.
A.frightened
B.annoyed
C.puzzled
D.disappointed -
单项选择题
I cannot（）your plan,for I see no money return for the pursuit.
A.argue with
B.approve of
C.rurn down
D.give up
