True
Consider the diagonals, AC and BD of quadrilateral ABCD.
They bisect each other at right angles.
∴ AC is the perpendicular bisector of line segment BD
⇒ AB = AD and CB = CD …(i)
And BD is the perpendicular bisector of line segment AC
⇒ AB = BC and AD = DC …(ii)
From (i) and (ii), we get
AB = BC = CD = AD
⇒ quadrilateral ABCD is a rhombus
Since, ABCD is a quadrilateral whose diagonals bisect each other at right angles and all four sides are equal.