If $$\frac{a}{b}{\text{ = }}\frac{c}{d}{\text{ = }}\frac{e}{f}{\text{,}}$$    then each of them is equal to = ?

$$\eqalign{ & {\text{Let,}} \cr & \frac{a}{b} = \frac{c}{d} = \frac{e}{f} = \frac{1}{2} \cr} $$
Now check from option to save your valuable time
$$\eqalign{ & {\text{Option D}} \cr & \frac{{a + 3c - 5e}}{{b + 3d - 5f}} \Rightarrow \frac{c}{d}\left[ {\frac{{\frac{a}{c} + 3 - \frac{{5e}}{c}}}{{\frac{b}{d} + 3 - \frac{{5f}}{d}}}} \right] \cr & \Rightarrow \frac{c}{d} = \frac{1}{2}\left( {{\text{Satisfy}}} \right) \cr} $$