If $f(x)= \left\{ \begin{array}{1 1} \frac{1- \sqrt 2 \sin x}{\pi-4x} & \quad if\;x \neq \frac{\pi}{4} \\ \alpha & \quad if\;x= \frac{\pi}{4} \end{array}. \right.$ is continuous at $\large\frac{\pi}{4},$ then $\alpha$ is equal to :

Question

$$\begin {array} {1 1} (a)\;4 & \quad (b)\;2 \\ (c)\;1 & \quad (d)\;1/4 \end {array}$$