The angle at which the axes are to be rotated to remove the $xy$ term in the equation $x^2 + 2\sqrt{3}xy = y^2$ is :

Question

( A ) $\frac{\pi}{2}$
( B ) $\frac{\pi}{6}$
( C ) $\frac{\pi}{4}$
( D ) $\frac{\pi}{3}$