Final answer:
The best method to confirm if all African lions are the same species is through a genetic analysis which provides information on DNA sequence and genetic markers, unlike phenotypic characteristics or behavior which can vary due to other factors.
Step-by-step explanation:
To determine whether all African lions are the same species, the most reliable and scientific approach would be to conduct a genetic analysis (Option A). Genetic analysis allows for the examination of the DNA sequence and the genetic markers that distinguish different species.
Such an analysis can reveal the genetic diversity within the population and confirm if all individuals belong to the same species or not. Alternatives like counting mane variations or measuring tail lengths are phenotypic characteristics that can vary due to environmental factors and may not necessarily correspond to different species.
Similarly, analyzing roar frequency could provide interesting behavioral data but is not a definitive method for determining species classification.