Question: In a Universal Subscriber Identity Module (USIM) application, when GSM access is enabled on a Mobile Equipment (ME) that supports GSM compact access technology, which of the following procedures are mandatorily performed if their respective services are enabled?
Option 1: Only Investigation Scan request
Option 2: Only CPBCCH information request
Option 3: Either Investigation Scan request or CPBCCH information request, depending on the ME's configuration
Option 4: Both Investigation Scan request and CPBCCH information request
Explanation: According to the specified conditions for GSM access initialization in a USIM application, if the applicable services are enabled and the Mobile Equipment (ME) supports GSM compact access technology, then both the Investigation Scan request (to scan for available networks or cells) and the CPBCCH information request (to obtain control channel information necessary for accessing the network) must be performed. This ensures the ME can properly initialize and connect to the GSM network.