In India, the term "Public Key Infrastructure" is used in the context of

Public Key Infrastructure (PKI) is a framework of technologies and policies used to manage digital certificates and public-key encryption, ensuring secure data transfer and authentication in digital transactions. While option (d) is a common distractor because PKI supports telecommunications, it is specifically a security protocol rather than general physical or network infrastructure. The core concept tested is the application of cryptography in digital security and cybersecurity.