What study design is this? in 1945, there were 1,000 women who worked in a factory painting radium dials on watches. the incidence of bone cancer in these women up to 1975 was compared to that of 1,000 women who worked as telephone operators in 1945. twenty of the radium dial painters and four of the telephone operators developed bone cancer between 1945 and 1975. a. cohort studyb. experimental studyc. clinical triald. cross-sectional studye. case-control study