Which statement about idle mode signaling reduction in the LTE network is true?
A. ISR support is not mandatory for UEs that support GERAN/UTRAN.
B. ISR requires special functionality on the UE and the core network nodes (MME, SGSN, and S-GW).
C. ISR requires special functionality on the UE and the core network nodes (MME and SGSN).
D. Gn/Gp SGSN supports idle mode signaling reduction functionality.
