In a quadrilateral ABCD,$\angle B=90^{\large\circ}$ and $AD^2=AB^2+BC^2+CD^2$,then $\angle ACD=$______

Question

$\begin{array}{1 1}60^{\large\circ}\\90^{\large\circ}\\45^{\large\circ}\\\text{None of these}\end{array} $