For two random variables XXX and YYY, what does Var(X+Y)=Var(X)+Var(Y)Var(X+Y) = Var(X) + Var(Y)Var(X+Y)=Var(X)+Var(Y) imply?
XXX and YYY are independent
Cov(X,Y)=0Cov(X, Y) = 0Cov(X,Y)=0
XXX and YYY have the same distribution
The correlation is 111