Consider the following: 1. Aarogya Setu 2. CoWIN 3. DigiLocker 4. DIKSHA Which of the above are built on top of open-source digital platforms?

Answer: D. All FOUR initiatives are built on top of open-source digital platforms. India's flagship Digital Public Infrastructure (DPI) is largely built on open-source stacks: (1) Aarogya Setu: COVID contact-tracing app launched in 2020. Open-sourced on GitHub in May 2020 (Android client first, then iOS and backend). One of the world's most widely used contact-tracing apps. (2) CoWIN: COVID vaccination platform. Open-source code released for adoption by other countries. India offered it as a public good — over 70 countries explored CoWIN. (3) DigiLocker: Cloud-based document repository platform launched in 2015 under Digital India. Open-source architecture; APIs published; states integrate with it. (4) DIKSHA (Digital Infrastructure for Knowledge Sharing): Open-source education platform launched in 2017 by Ministry of Education. Built on the open-source Sunbird framework, used by school education boards across states. All four are explicitly open-source DPI platforms, part of India's contribution to global digital public goods. Source: MeitY / Department of School Education and Literacy / Sunbird platform documentation.