选择题:甲乙丙三人参加 2022 年冬奥会北京、 延庆、 张家口三个赛区志愿服务活动, 若每人只能选择一个赛区, 且选择其中任何一个赛区是等可能的. 记 X 为三人选中

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甲乙丙三人参加 2022 年冬奥会北京、 延庆、 张家口三个赛区志愿服务活动, 若每人只能选择一个赛区, 且选择其中任何一个赛区是等可能的. 记 X 为三人选中的赛区个数, Y为三人没有选中的赛区个数, 则()

A.E(X) =E(Y), D(X) =D(Y)

B.E(X) =E(Y), D(X) ≠D(Y)

C.E(X) ≠E(Y), D(X) ≠D(Y)

D.E(X) ≠E(Y), D(X) =D(Y)

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