Ken Is Conducting a Qualitative Study for the University Regarding

Ken is conducting a qualitative study for the university regarding the institutional variables that racial and ethnic minority doctoral students face in completing their degrees. He feels he needs to interview about 35 graduates. He interviews a small initial sample identified though formal complaints filed regarding the issue. He then asks each of those he interviews to identify any additional participants they can think of and then interviews those individuals until he has reached his sample size. Ken is best illustrating

A) random purposive sampling.
B) systematic sampling.
C) intensity sampling.
D) snowball sampling.