Question: Upon receiving a 'SET UP CALL' command from the UICC, if the Mobile Equipment (ME) is unable to process the command due to its current engagement in a Supplementary Service (SS) transaction, how does the ME inform the UICC?
Option 1: TERMINAL RESPONSE (ME unable to process command - currently busy on call)
Option 2: TERMINAL RESPONSE (ME unable to process command - currently busy on SS transaction)
Option 3: NETWORK CURRENTLY UNABLE TO PROCESS COMMAND
Option 4: COMMAND BEYOND ME'S CAPABILITIES
Explanation: This is the correct response because, according to specifications, if the ME is busy with an SS transaction when it receives a 'SET UP CALL' command, it specifically uses this response to inform the UICC, allowing for precise communication of the reason for the command rejection.