Your Answer is

Correct Answer is B

Explanation

After connecting AD, BE, and FC, you can see that these three lines divide the central angle into six equal angles, so each angle is one-sixth of 360 degrees, that is, 60°. Let the center of the circle be O, in △ABO, ∠AOB = 60°, AO=BO, so this is an equilateral triangle, AB = AO = r = d/2 = 9/4