单项选择题

以下关于危险度评定的叙述中，哪条不正确

A.早期用于放射线及致癌物的评定，现用于其他化学物的评定
B．确定最大耐受剂量是评定的关键
C．具有可预测性
D．属定量评定
E．用动物毒性资料向人的危险性外推时多应用适当的数学模型

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单项选择题

M：Our school has just built some new apartments near campus，but one bedroom runs for 500dollars a month.W：That’s a bit beyond the reach of most students!Q：What does the woman mean？（）

A．The new apartments can accommodate 500students.
B．The new apartments are not available until next month.
C．Most students can’t afford to live in the new apartments.
D．It takes only 5minutes to reach the campus from the apartments.

单项选择题

电路如图所示，已知含源二端网络N的戴维南等效电阻R0=1Ω，当RL=4Ω时，电流表的读数为2A，当RL=9Ω时，表的读数为( )。 A．1.5AB．0.8AC．1AD．1.2A

A.shangxueba.cn/images/2010q3/ct_jggysbnjxj_jggysbnjxchoose_0398(106).jpg'
B.1.5A
B．0.8A
C．1A
D．1.2A