A set of three points is chosen randomly from the grid shown. Each three-point set has the same probability of being chosen. What is the probability that the points lie on the same straight line?
Answer Choices
A. \dfrac{1}{21}
B. \dfrac{1}{14}
C. \dfrac{2}{21}
D. \dfrac{1}{7}
E. \dfrac{2}{7}