The angle between the curves $y^2=4x, \; x^2 = 4y$ at $(4,4)$, is :

Question

( A ) $\tan^{-1} (\frac{1}{2})$
( B ) $\frac{\pi}{4}$
( C ) $\frac{\pi}{2}$
( D ) $\tan^{-1} (\frac{3}{4})$