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A group of researchers wants to investigate the association between exhaust fumes (exposure) and asthma (outcome). They enrolled 1000 subjects who had asthma into the study. They want to frequency-match controls to the cases on a 4 to 1 basis (i.e. 4 controls to 1 case) by race-ethnicity. The following table presents the raceethnicity distribution table of the cases Race and Ethnicity Cases Non-Hispanic White 450 Non-Hispanic Black I 225 Hispanic Others How many Non-Hispanic White controls can they enroll in the study? 0 a)1800 " b)900 T c)1000 7 d) 300