Semicircles P O Q and R O S pass through the center of circle O. What is the ratio of the combined areas of the two semicircles to the area of the circle O ?
Answer Choices
A. \dfrac{\sqrt{2}}{4}
B. \dfrac{1}{2}
C. \dfrac{2}{\pi}
D. \dfrac{2}{3}
E. \dfrac{\sqrt{2}}{2}