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【简答题】
袋中有 5 个球 , 其中 3 个红球 2 个白球 . 现从袋中不放回地连取两个 . 已知第一次取得红球时 , 求第二次取得白球的概率 .
参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【单选题】第二篇 Sleep We all know that the normal human daily cycle of activity is of some 7 - 8 hours’ sleep alternating with some 16 - 17 hours’ wakefulness and that, broadly speaking, the sleep n...
A.
people hate the inconvenience of working on night shifts.
B.
your life is disturbed by changing from day to night routines and back.
C.
not all industries work at the same hours.
D.
it is difficult to find a corps of good night workers.