Molecular Data Can Be Used to Assess Relationships Among the Major

Molecular data can be used to assess relationships among the major groups of living organisms whose common ancestors lived millions or billions of years ago. Similar techniques can be used to assess relationships among populations within a species. How can molecular techniques be useful for such varied comparisons?

A) Studying the relationships among different populations of a single species can be just as effective as studying the relationships of major biological groups if you look at a lot more genes.
B) Faster-evolving gene sequences provide better data for comparisons among close relatives, whereas very slowly evolving sequences work best for distantly related taxa.
C) The relationships between very different groups, such as bacteria and whales, are assessed using mtDNA sequences, whereas rRNA sequences are used for very closely related groups.