Question: What is the primary purpose of the Validity-Period information element in an SMS-SUBMIT from a Mobile Station (MS) to a Short Message Service Center (SC)?
Option 1: To specify the priority level of the short message for delivery.
Option 2: To indicate the preferred delivery time window to the recipient.
Option 3: To set the maximum number of delivery attempts by the SC.
Option 4: To define the time period for which the SC must store the message before delivery.
Explanation: The Validity-Period informs the SC about the duration to retain the short message, ensuring its availability until successful delivery. This relates to storage and guarantee of existence, rather than priority, timing of delivery, or number of attempts.