Six pepperoni circles will exactly fit across the diameter of a 12-inch pizza when placed as shown. If a total of 24 circles of pepperoni are placed on this pizza without overlap, what fraction of the pizza is covered by pepperoni?
Answer Choices
A. \dfrac{1}{2}
B. \dfrac{2}{3}
C. \dfrac{3}{4}
D. \dfrac{5}{6}
E. \dfrac{7}{8}