For each n e N. define the hypercube graph, to have vertices f0, 1(t-bit strings) and edges between bit-strings u and v if they differ in only one bit (for example. 010 and 000 are adjacent. but 110 and 011 are not). Then the distance between two strings a, y in the hypercube graph is not: OAlways less than or equal to n. The difference between the number of 1's in z and the number of 1's in y. The number of 1's in the string z Dy. The number of bits that we need to change to transform z into y