If x + 16x = 8, then the value of x^2 + 32x^2 is:

Answer: Option D

$$\begin{array}{rl}& x+\frac{16}{x}=8\\ & \text{at }x=4\text{ it satisfy}\\ & x^2+\frac{32}{x^2}=4^2+\frac{32}{4^2}\\ & =16+2\\ & =18\end{array}$$