What Is the Best Reason (Most Useful Reason for the Largest

What is the best reason (most useful reason for the largest number of people) why having the ability to recognize differing strains of HIV-1 would aid in epidemiological studies?

A) Since HIV mutates so rapidly, being able to trace different strains allows us to better trace who gave the virus to whom first. This is especially useful in legal issues related to intentional HIV infection.
B) It doesn't-HIV is HIV. It doesn't matter which strain a person has-it only matters that we know who is infected and who isn't.
C) By recognizing different strains, we can fine-tune the treatments for each individual to best suppress the progress of the illness.
D) Being able to observe how the virus mutates as it progresses through a population of susceptible individuals, some of whom are treated and some of whom have not been treated, allows us to better understand how the virus changes over time in order to better fight it with new drugs/therapies.