If 0 is the angle between the curves $xy=2$ and $x^2+4y=0$ and $x^2+4y=0$, then $\tan \theta$ is equal to :

Question

\[\begin {array} {1 1} (a)\;1 & \quad (b)\;-1 \\ (c)\;2 & \quad (d)\;3 \end {array}\]