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【单选题】
袋中有a只黑球，b只白球，从中依次无放回地摸三次，每次摸一球，仅第二次摸得黑球的概率为
A.
A.AB2
B.
A.CB2
C.
1-A.AB2
D.
1-A.AC2
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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.