Answer:
An equilateral triangle inscribed in a circle Â
Step-by-step explanation:
A. An equilateral triangle circumscribed about a circle
 equilateral triangle circumscribed about a circle mean a circle inside an equilateral triangle. We don't have circle inside the triangle in our graph.
B. An equilateral triangle inscribed in a circle Â
Yes equilateral triangle is inscribed in a circle BDE
C. The circumcenter of an equilateral triangle
Circumcenter is not equidistant from the vertices of triangle