PASCAL 2005 Problem 20

Harry the Hamster is put in a maze, and he starts at point S. The paths are such that Harry can move forward only in the direction of the arrows. At any junction, he is equally likely to choose any of the forward paths. What is the probability that Harry ends up at B?

Answer Choices
A. \frac23
B. \frac{13}{18}
C. \frac{11}{18}
D. \frac13
E. \frac14