The speaker，________for his speeches，was warmly received by the students．
A. known
B. to be known
C. having known
D. being known
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During the Ice Ages，man developed the use of tools，and this is a way of protecting himself
A. conflicts
B. hazards
C. faults
D. shortcomings
函数y=2x3-x2+1在x=1处的导数为（） (A)2 (B)3 (C)4 (D)5
Work hard ________ you will overcome the difficulties．
A. so
B. and
C. for
D. but
A.inB.likeC.forD.as
A. in
B. like
C. for
D. as
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