Question: What action is taken when a receiving entity (MME or VLR) detects a syntactically or semantically incorrect message, and what additional step is performed regarding the O&M entity?
Option 1: The entity ignores the error and continues with the current procedure; no notification to the O&M entity is required.
Option 2: The entity sends an SGsAP-STATUS message but only if the error is syntactical, and informs the O&M entity upon sending.
Option 3: The entity abandons the related procedure, returns to its previous state, sends an SGsAP-STATUS message (including the erroneous message), and notifies the O&M entity.
Option 4: The entity corrects the error automatically without notifying the O&M entity or sending an SGsAP-STATUS message.
Explanation: This is the correct answer because, according to the error handling procedures outlined in the specification, when a receiving entity detects an error (either syntactical or semantical), it must abandon the procedure related to the incorrect message, return to its previous state, and send an SGsAP-STATUS message that includes the IMSI information element value (if applicable) and the erroneous message itself. Additionally, both the sending and receiving entities are required to inform the O&M entity upon sending or receiving an SGsAP-STATUS message, ensuring transparency and logging of error events for operational and maintenance purposes.