In an epidemiological study, the first case which comes to the attention of the investigator is

Ans. is 'b'i.e. Index case Epidemiological terminologyPrimary case - is the first case of a communicable disease introduced into the population unit under study.Index case - is the first case, that comes to the attention of the investigator, it is not always the primary case.Secondary cases - are those cases arising d/t contact with the primary case.