Two species belonging to the same genus are identical in morphology which of the following structural characteristics is more useful in distinguishing such species

Two species belonging to the same genus are identical in morphology. Chromosome number and morphology are the structural characteristics that are more useful in distinguishing such species.
Similar DNA sequences, biogeographical features, ecological features, and morphological features of the organisms can be used to rank them in a particular genus.
The chromosome number of each species is different and based on which they can be easily segregated.