Trong các tính chất sau, tính chất nào sai? 0 < a < b => a/d < b/c

A. $\left\{\begin{array}{c}0<a<b\\ 0<c<d\end{array}\right.\Rightarrow \frac{a}{d}<\frac{b}{c}$

B. $\left\{\begin{array}{c}a<b\\ c<d\end{array}\right.\Rightarrow a-c<b-d$

C. $\left\{\begin{array}{c}a<b\\ c<d\end{array}\right.\Rightarrow a+c<b+d$

D. $\left\{\begin{array}{c}0<a<b\\ 0<c<d\end{array}\right.\Rightarrow ac<bd$