Which one of the following links all the ATMs in India ?

The National Payments Corporation of India (NPCI) is the correct answer because it operates the National Financial Switch (NFS), the largest network of shared ATMs in India that facilitates inter-bank transactions and interoperability. While the Reserve Bank of India (Option d) is the central regulator that oversees the banking sector, it does not directly manage the operational infrastructure for retail payments. The core concept being tested is the institutional framework of India’s retail payment and settlement systems.