If $\cot\theta,cosec \theta$ are the roots of the equation $ax^2+bx+c=0$ and $\Delta=b^2-4ac$,then $a^4$ equals

Question

$\begin{array}{1 1}(A)\;bc\Delta&(B)\;c\Delta\\(C)\;b^2\Delta&(D)\;b\Delta\end{array}$