If y = 4x , then x^2y is = ?

Answer: Option B

$$\begin{array}{rl}& \iff \sqrt{y}=4x\\ & \iff y={\left(4x\right)}^2\\ & \iff y=16x^2\\ & \iff \frac{x^2}{y}=\frac{1}{16}\end{array}$$