For positive integers n, denote by D(n) the number of pairs of di erent adjacent digits in the binary (base two) representation of n. For example, D(3) = D(112) = 0, D(21) = D(101012) = 4, and D(97) = D(11000012) = 2. For how many positive integers n less than or equal to 97 does D(n) = 2? (A) 16 (B) 20 (C) 26 (D) 30 (E) 35