Final answer:
Rathnam likely used the 1989 Scheduled Castes and Scheduled Tribes (Prevention of Atrocities) Act to file a complaint due to social discrimination.
Step-by-step explanation:
Rathnam likely used the 1989 Scheduled Castes and Scheduled Tribes (Prevention of Atrocities) Act to file a complaint due to social discrimination. The act was implemented by the Indian government to protect the rights and prevent the atrocities faced by marginalized communities, including Dalits and Tribes. These communities have historically been subjected to discrimination and oppression based on their caste and tribal status, resulting in various forms of abuse and violence.