Cluster testing technique is useful in which of the following conditions?

Explanation: Following methods are used for case detection of STD: * CONTACT TRACING: Contact tracing is the term used for the technique by which the sexual paners of diagnosed patients are identified, located, investigated, and treated. * CLUSTER TESTING: Here the patients are asked name other persons of either sex who move in the same socio-sexual environment. These persons are then screened. Ref: Park's textbook of Preventive and Social Medicine, 21stedition, Page 313