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举一反三
【单选题】Ladies and gentlemen, welcome to Dalian, a famous summer resort ( 避暑胜地 ) and one of the best tourist cities in China. With clear sky, green mountains, blue seas, fine beaches, clean streets and lovely...
A.
comes in the best season.
B.
is here to join more tourists
C.
may not stand the heat here.
D.
is traveling back home.
【单选题】平均致死剂量（D0）是指（）。
A.
杀死95%细胞的剂量
B.
杀死80%细胞的剂量
C.
杀死63%细胞的剂量
D.
杀死37%细胞的剂量
E.
杀死50%细胞的剂量