What will the Professor Zhou do
A. He will be away.
B. He will meet LILI.
C. He is rude.
When was the building built
A. Seven years ago.
B. Twenty years ago.
C. Twelve years ago.
设随机变量X～N(0，4)，Y服从参数λ=0.5的指数分布，Coy(X，Y)=-1，令Z=X-aY已知Coy(X，Z)=Cov(Y，Z)。 求X与Z的协方差矩阵的逆矩阵。
预应力筋因锚具夹持作用发生疲劳破坏的截面面积不应大于试件总截面面积的10%。
A. 对
B. 错
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