Milk ring test is done for:

Ans. is 'a' i.e., BrucellosisDiagnosis of infect animal by Milk ring test - In this a sample of whole milk is mixed with a drop of stained brucella antigen. (A concentrated suspension of killed brucella abortus stained with hematoxylin) and incubated in water bath at 70degC for 40 to 50 minutes. If antibodies are present in the milk the bacilli are agglutinated and rise with the cream to form a blue ring at the top, leaving the milk unstained. If the antibodies are absent no ring is formed and the milk remains uniformly blue.