A.\(\left\{ \begin{array}{l}a < b\\c > d\end{array} \right. \Rightarrow a + c < b + d\)
B.\(\left\{ \begin{array}{l}a < b\\c > d\end{array} \right. \Rightarrow a + c > b + d\)
C.\(\left\{ \begin{array}{l}a > b\\c > d\end{array} \right. \Rightarrow ac > bd\)
D.\(\left\{ \begin{array}{l}a > b\\c > d\end{array} \right. \Rightarrow a + c > b + d\)