Naming the circle is just the only point in the center of the circle (E). The radius is half diameter of the circle so imagine a line connecting the center dot to any dot to the outside. An example of this would be (EC). The diameter is half the circle so any 3 points that cut the circle in half. This could be either (DEC) or (AEB).
So the answers would be:
A: (E)
B: (EC)
C: (DEC)
D: (AEB)
