If the diameter is 6, then that means that each segment on the diameter of the circle is 1 and there’s a radius of 3.
Whole circle = 9 pi
Then you find the area of the non-shaded portions:
Area of the non-shaded semicircle from A to C is 4 pi divided by 2, so = 2 pi.
Area of the other non-shaded semicircle from B to D is also 2 pi, but then you look at the small blue semicircle from C to D which has an area to be 1 pi. Thus, the non-shaded semicircle from B to D is 2 pi - 1 pi = 1 pi.
2 pi + 1pi = 3 pi
Subtract 3 pi from the whole circle 9 pi to get 6 pi, which is letter ©.