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【单选题】March Madness For the rest of the month, an epidemic (流行病) will sweep across the US．It will keep kids home from school．College students will ignore piles of homework．Employees will suddenly lose their...
A.
Many Americans will be sent to madhouses.
B.
Great excitement will spread across the US.
C.
About 20 million Americans will be put in prison.
D.
A deadly epidemic will break out in the US.
【单选题】 March Madness For the rest of the month, an epidemic (流行病) will sweep across the US. It will keep kids home from school. College students will ignore piles of homework. Employees wil...
A.
Many Americans will be sent to madhouses
B.
Great excitement will spread across the US
C.
About 20 million Americans will be put in prison
D.
A deadly epidemic will break out in the US
【单选题】一盒中置有黑球5个、红球4个,自其中连续抽取4球,令随机变量X代表抽出黑球的个数,试求E(x)=:
A.
0.357
B.
0.753
C.
2.222
D.
0.617