For positive integers n, denote by D(n) the number of pairs of different adjacent digits in the binary (base two) representation of n. For example, D(3) \equal{} D(11_2) \equal{} 0, D(21) \equal{} D(10101_2) \equal{} 4, and D(97) \equal{} D(110001_2) \equal{} 2. For how many positive integers n less than or equal to 97 does D(n) \equal{} 2?<spanclass=′latex−bold′>(A)</span>16<spanclass=′latex−bold′>(B)</span>20<spanclass=′latex−bold′>(C)</span>26<spanclass=′latex−bold′>(D)</span>30<spanclass=′latex−bold′>(E)</span>35