Answer: 3. Structure is a better indicator of a relationship between two organisms because function can be caused by environment, not common ancestry. Structure is better than function because the structure is based on genetics. For example, the wings on a fly and the wings on a bird perform the same function, but their genetic bases are different. However, the wings on a bird and the arms on a primate are coded by similar genes even though the functions are different.
The best measure of relatedness is the underlying genomic DNA.
Step-by-step explanation: