The distance between the point $(qa \sin \alpha , a \cos \alpha )$ and $( a \cos \alpha, -a \sin \alpha)$ is

Question

$\begin{array}{1 1}(A) \;2a\;units\\(B)\;\sqrt 2 a\;units \\(C)\;2\sqrt a units \\(D)\;none\;of \;the\;above \end{array}$