Question 4 - iv) In this experiment from Sallusto et al. 1994, "Two subsets of memory T lymphocytes with distinct homing potential and effector functions", an additional treatment that would make these data more convincing would be to… (Select only ONE answer). Justify your answer. a. Add a positive control of CD45RA-CCR7- memory T cells b. Add a negative control of NK cells c. Add a negative control of CD45RA-CCR7- memory T cells d. Add a positive control of CD45RA-CCR7+ memory T cells