101 On the plane, point $P$ is equidistant from the four vertices of a convex quadrilateral. Then the position of point $P$ is suitable for
A. Inside the quadrilateral
B. On the boundary of the quadrilateral
C. Outside the quadrilateral
D. All three situations are possible
101 D. Consider a circle with center $P$, and quadrilateral $A B C D$ is its inscribed quadrilateral.