From a regular octagon, a triangle is formed by connecting three randomly chosen vertices of the octagon. What is the probability that at least one of the sides of the triangle is also a side of the octagon?
Answer Choices
A. \dfrac{2}{7}
B. \dfrac{5}{42}
C. \dfrac{11}{14}
D. \dfrac{5}{7}
E. \dfrac{6}{7}