Let $a,$ $b,$ $c,$ and $d$ be real numbers such that $a > b$ and $c > d.$ Enter the letters of the statements below that must be true.

(A) $a + c > b + d.$

(B) $2a + 3c > 2b + 3d.$

(C) $a - c > b - d.$

(D) $ac > bd.$

(E) $a^2 + c^2 > b^2 + d^2.$

(F) $a^3 + c^3 > b^3 + d^3.$