Question: In a GSM security context, what is the prerequisite for a USIM to perform operations such as computing RES, CK, and IK?
Option 1: Service n°38 being "available"
Option 2: Successful authentication with the LTE network
Option 3: Presence of a specific IMSI (International Mobile Subscriber Identity)
Option 4: Completion of a previous UMTS (Universal Mobile Telecommunications System) security procedure
Explanation: For a USIM to engage in GSM security context operations like computing Response (RES), Cipher Key (CK), and Integrity Key (IK), the essential condition is that Service n°38 must be "available". This service availability is crucial for initiating these security-related computations within the USIM, ensuring secure communication in the GSM network.