The answer would be: A. Mitochondrial DNA is beneficial in both of these cases
Unlike nuclear DNA, the mitochondrial DNA(mtDNA) can be found in the mitochondrial. Mitochondrial DNA only inherited from mother, so it's relatively unchanged than nuclear DNA that mixed from father and mother. Mitochondrial DNA has higher mutation rate in animals because it doesn't have repair mechanism like nuclear DNA. These mutations can be used as a clue for how close the relation of an organism to others.These attributes make analyzing the ancestral relationship of organisms that closely or distantly related easier.
