Which two species are likely to have the most similar dna base sequences?

Based on the attached Image;
The two species that are likely to have the most similar DNA base sequences are C and D. 
An evolutionary tree or a phylogenetic tree, like the one shown on the image is used to indicate which ancestors gave rise to which descendants. The tree represents the evolutionary relationships among a set of organisms or groups of organisms, called taxa. The tips of the tree represents groups of descendant taxa and the nodes represents the common ancestors of these descendants.