If $\alpha+\beta=\large\frac{\pi}{2}$ and $\beta+\gamma=\alpha$ then $\tan \alpha$ equals

Question

$\begin{array}{1 1}(a)\;2(\tan\beta+\tan\gamma)&(b)\;\tan\beta+\tan\gamma\\(c)\;\tan\beta+2\tan\gamma&(d)\;2\tan\beta+\tan\gamma\end{array}$