题目8.(单选题,7分) 若D(X)=25,D(Y)=36,rho_(XY)=0.4,则D(X-Y)=(......)A. 61B. 73C. 49D. 378.(单选题,7分) 若$D(X)=25,D(Y)=36,\rho_{XY}=0.4$,则$D(X-Y)=(\cdots\cdots)$A. 61B. 73C. 49D. 37题目解答答案D. 37