The long island breast cancer study tested the hypothesis that environmental pollution was causing the relatively high rates of breast cancer among residents of suffolk and nassau counties of new york. epidemiologists identified a group of 1,420 women who were diagnosed with breast cancer between 1984 and 1986 and compared their residential histories over a 20 year period with those of a matched group of healthy women. what kind of epidemiologic study was this? a) cohortb) interventionc) case-controld) prospective