Consider a circle with centre \(O\). Line segments \(BD\) and \(AC\) are two perpendicular diameters of the circle. What is the figure \(ABCD\)? Reason and/or experiment to figure this out.
 
Answer:
 
The figure \(ABCD\) is a
 
Reason:
 
(Note: Select \(1\) or more choices if necessary.)