Question: In a UE utilizing GBA with OSCORE support, where is the shared key **Ks_ext_NAF** used as the shared key between the UE and the NAF?
Option 1: When the CoAP client supporting OSCORE resides in the Mobile Equipment (ME)
Option 2: When the CoAP client supporting OSCORE resides in the Universal Integrated Circuit Card (UICC)
Option 3: When both ME and UICC host a CoAP client supporting OSCORE
Option 4: Never, as Ks_int_NAF is always used for OSCORE
Explanation: According to GBA specifications for UE requirements, when the CoAP capable client that supports OSCORE is located in the Mobile Equipment (ME), the shared key **Ks_ext_NAF** is utilized between the User Equipment (UE) and the Network Application Function (NAF), ensuring secure communication in the context of Generic Bootstrapping Architecture.