设X₁和X₂分别表示掷两颗骰子各出现的点数，则有( )。

A．X<SUB>1</SUB>+X<SUB>2</SUB>=2X<SUB>2</SUB>
B．E(X<SUB>1</SUB>)+E(X<SUB>2</SUB>)=2E(X<SUB>1</SUB>)
C．Var(X<SUB>1</SUB>)+Var(X<SUB>2</SUB>)=2Var(X<SUB>1</SUB>)
D．Var(X<SUB>1</SUB>X<SUB>2</SUB>)=4Var(X<SUB>1</SUB>)
E．E(X<SUB>1</SUB>)+E(X<SUB>2</SUB>)=3E(X<SUB>1</SUB>)