Question: In SMS, what indicates that a reply path exists for a Short Message originated from a Mobile Station?
Option 1: Presence of the TP-Destination-Address parameter in the SMS-SUBMIT PDU
Option 2: Setting of the TP-Reply-Path parameter in the SMS-SUBMIT PDU of the original MT SM
Option 3: Absence of the TP-Reply-Path parameter in the SMS-DELIVER PDU of the original MT SM
Option 4: Presence of the TP-Reply-Path parameter in the SMS-DELIVER PDU of the original MT SM
Explanation: A reply path exists if the TP-Reply-Path parameter was set in the SMS-DELIVER PDU of the original Mobile Terminated Short Message, indicating to the receiving MS that a return path for responses is available.