A.1
B.2
C.3
D.4
[单选题]A.1B.2C.3D.4
[判断题]A.对B.错
[单选题]A.B.C.D.
[单选题]A.≤1/4B.≤8/9C.≤80/81D.≥8/9
[单选题]A.线性相关B.线性无关C.正交D.平行
[单选题]A.S是σ的无偏估计B.C.D.