For a better understanding of the explanation provided here, please find the diagrams in the two files that have been attached.
As can be clearly seen from the diagram, PR and QS are the diameters of the circle and they intersect each other at the centre, O of the circle.
The angle these diameters make at the point of intersection O is 90 degrees.
If Margot joins the points P,Q,R and S which are on the circumference of the circle, then we will get a square with sides PQ, QR, RS and SP as shown in the second diagram.
Thus, the correct option is Option A.
