Question: In a 5G System, when the Network Exposure Function (NEF) notifies an Application Function (AF) about the status of a previously submitted group message delivery using the `Nnef_MBSGroupMsgDelivery_StatusNotify` service operation, how is the AF expected to acknowledge successful reception?
Option 1: By sending a response message with an HTTP "200 OK" status code and including the received status in the response body.
Option 2: By sending a `Nnef_MBSGroupMsgDelivery_StatusNotify` response message with an HTTP "204 No Content" status code.
Option 3: Through a separate, subsequent HTTP POST request to the NEF confirming receipt.
Option 4: The AF does not send any acknowledgement for successful reception.
Explanation: According to the specified procedure for MBS Group Message Delivery Status Notification in the context of 5G System Northbound APIs, upon successfully receiving a notification request from the NEF, the AF is expected to acknowledge this by sending a response with an HTTP "204 No Content" status code. This indicates that the request has been successfully processed without needing to return any content in the response body, which aligns with the nature of an acknowledgement for receipt notification.