51. a random walker travels along a one- dimensional discrete lattice (labelled by points -n, -n+1, .0, .. n- 1, n) by putting random steps of length i unit tow

51. A random walker travels along a one- dimensional discrete lattice (labelled by points -N, -N+1, .0, .. N- 1, N) by putting random steps of length I unit towards left or right. If the initial position is zero, the probability of finding the walker at the 0 position in a 6 step walk is 9 (A) 256 5 (B) 18 (C) D) 16