If x2 + 4y2 = 4xy, then x : y is -

Answer: Option C

$$\begin{array}{rl}& =x^2+4y^2=4xy\\ & \Rightarrow x^2-4xy+4y^2=0\\ & \Rightarrow \left(x-2y^2\right)=0\\ & \Rightarrow x=2y\\ & \Rightarrow \frac{x}{y}=2\\ & \Rightarrow x:y=2:1\end{array}$$