If $\alpha,\beta$ are roots of $ax^2+bx+c=0$ then $\lim\limits_{x\to \alpha}\large\frac{1-\cos(ax^2+bx+c)}{(x-\alpha)^2}$ is

Question

$\begin{array}{1 1}(a)\;(a-b)^2&(b)\;\large\frac{(\alpha-\beta)^2}{2}\\(c)\;\big(\large\frac{\alpha(\alpha-\beta)}{2}\big)^2&(d)\;\text{None of these}\end{array}$