Question: In SMS according to 3GPP standards, what does the first '#' character encountered in the TP-Destination-Address (TP-DA) field indicate?
Option 1: The start of subaddress digits that are used for additional routing information.
Option 2: The termination of the main destination phone number part, separating it from SMS content.
Option 3: The beginning of an optional parameter for message prioritization.
Option 4: An error in the formatting of the TP-DA field.
Explanation: According to 3GPP standards, the first '#' character in the TP-Destination-Address (TP-DA) field marks the end of the SMSC routing address and signifies the start of subaddress digits for additional routing or informational purposes.