In a triangle ABC $\begin{vmatrix} a^2& b\sin A & C\sin A\\b\sin A&1&\cos(B-C)\\C\sin A&\cos (B-C) & 1\end{vmatrix}$ equals

Question

$\begin{array}{1 1}(A)\;\sin A-\sin B\sin C&(B)\;abc\\(C)\;1&(D)\;0\end{array}$