Question: What is the primary purpose of the `CatSendShortMessage` function in a (U)SIM API?
Option 1: To retrieve incoming SMS messages from the network
Option 2: To update the icon gallery on the User Equipment (UE)
Option 3: To establish a voice call using the provided number and TON/NPI
Option 4: To issue a SEND SHORT MESSAGE proactive command to send an SMS
Explanation: The `CatSendShortMessage` function initiates sending of a short message (SMS) by issuing a SEND SHORT MESSAGE proactive command, involving parameters for constructing and sending an SMS. The other options do not align with this behavior.