Exp) Option d is the correct answer.

“Closed source” software has source code that only the person, team, or organization who created it and maintains exclusive control over. But Open source software is software with source code that anyone can inspect, modify, and enhance.

Some examples of public services being delivered through systems that use FOSS building blocks, including Aadhaar, GSTN , and the DigiLocker.

Many other solutions launched by the government including Digilocker, Diksha, Aarogya Setu, the Covid-19 vaccination platform CoWIN have also been built on top of open-source digital platforms.

Source: https://forumias.com/blog/free-and-open-source-software-foss-has-great-potential-in-government-applications/

https://www.thehindu.com/sci-tech/technology/aarogya-setu-app-is-now-open-source-what-does-it-mean/article31689459.ece

https://indianexpress.com/article/opinion/columns/free-and-open-source-software-linux-user-groups-aadhaar-gstn-digilocker-7477122/

https://www.business-standard.com/article/technology/game-changer-making-sense-of-open-source-software-in-digital-economy-121071100882_1.html