When a tiny circular is placed in the path of light from a distant source, a bright spot in seen at the center of the shadow of the obstacle . explain why ?

Question

$\begin{array}{1 1} \text{due to constructive interference } \\ \text{due to destructive interference } \\ \text{due to diffraction angle being very large } \\ \text{due to diffraction angle being very small } \end{array} $