Suy luận nào sau đây đúng:

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

B. \(\left\{ \begin{array}{l}
a > b\\
c > d
\end{array} \right. \Rightarrow \frac{a}{c} > \frac{b}{d}\)

C. \(\left\{ \begin{array}{l}
a > b\\
c > d
\end{array} \right. \Rightarrow a - c > b - d\)

D. \(\left\{ \begin{array}{l}
a > b > 0\\
c > d > 0
\end{array} \right. \Rightarrow ac > bd\)