Point O is the center of the regular octagon A B C D E F G H, and X is the midpoint of side \overline{A B}. What fraction of the area of the octagon is shaded?
Answer Choices
A. \dfrac{11}{32}
B. \dfrac{3}{8}
C. \dfrac{13}{32}
D. \dfrac{7}{16}
E. \dfrac{15}{32}