Scientists recently revised the classification of the red panda (Ailurus fulgens). They based their revision on comparisons of data obtained from
the red panda and other species. Which type of data provided the STRONGEST evidence for the revised classification?
A. analysis of DNA sequences
B. observations of behaviors
C. measurements of body structures
D. descriptions of food sources and habitats

Classification is the assortment or arrangement of living organisms into groups on the basis of their similarities. These groups into which organisms are classified are called taxonomic groups or taxon.

Before the 1960s, scientists solely relied on phenotypic or physical characteristics of organisms to classify them into related taxonomic groups.
Modern DNA sequencing methods are capable of revealing similarities and differences between organisms on the level of genes or DNA sequences. Therefore, DNA sequence analysis is the most accurate method for classification.
Closely related organisms have specific genes with the same DNA sequence. These sequences, known as conserved sequences, can be found universally in all species of a particular organism. For example, in bacteria, a DNA sequence known as the 16s RNA is conserved in related species. 16s RNA analysis is widely used to identify and classify bacteria.
Behaviors, body structure, habitat and food choices are all phenotypic characters that do not provide definite evidence of evolutionary relationship.
Different species can have the same habitat, behavior, anatomy and morphology.