[问答题]
[单选题]A.π/6B.π/4C.π/3D.π/2
[单选题]A.0B.C.D.
[判断题]对错A.对B.错
[单选题]方差σ2/x有:()。A.B.C.D.
[单选题]方差σ2/x有:()。A.B.C.D.
[问答题]___________。