Question: What is the primary condition under which the Service Centre (SC) relinquishes responsibility for a submitted short message to a Mobile Station (MS)?
Option 1: Upon receiving acknowledgement from the MS that the message has been read.
Option 2: When either a delivery report is received or the Validity-Period of the message expires, whichever occurs first.
Option 3: Immediately after forwarding the message to the serving Mobile Switching Centre (MSC).
Option 4: Once the SC confirms the MS's location with the Home Location Register (HLR).
Explanation: This option correctly reflects the requirement for when an SC can consider its responsibility for a message fulfilled. The condition of either receiving a delivery report or the expiration of the Validity-Period aligns with efficient and reliable message handling practices in telecom networks, ensuring messages are not indefinitely retained without resolution.