ఆబోతు మూపురం.

వివరణ

This riddle (ఆబోతు మూపురం) refers to a 'window' or 'opening in a wall' — the answer is apt because a window literally has an 'open mouth' (ఆబోతు) that is 'closed' (మూపురం) by shutters or panes, embodying this paradox.