If 3a + 4b3c + 4d = 3a - 4b3c - 4d then

Answer: Option B

$$\begin{array}{rl}& \text{According to question,}\\ & \frac{3a+4b}{3a-4b}\text{ = }\frac{3c+4d}{3c-4d}\\ & \Rightarrow \frac{3a}{4b}=\frac{3c}{4d}\\ & \Rightarrow ad=bc\end{array}$$