If the angles made by a straight line with the coordinate axes are $\alpha,\large\frac{\pi}{2},$$-\alpha, \beta$ then $\beta=$

Question

$$\begin {array} {1 1} (a)\;0 & \quad (b)\;\frac{\pi}{6} \\ (c)\;\frac{\pi}{2} & \quad (d)\;\pi \end {array}$$