Question: In SMS (Short Message Service) as per 3GPP standards, how can the subject field be delimited or indicated in a message to ensure full compatibility across MO (Mobile Originated) and MT (Mobile Terminated) messages?
Option 1: Only by using square brackets [] around the subject, immediately following the to-address.
Option 2: Exclusively by prefixing the subject with 'SUB:' and separating it from the message with a semicolon (;).
Option 3: Either by enclosing the subject in angle brackets <> or by suffixing the to-address with a hyphen (-) before the subject.
Option 4: By using either round brackets () to enclose the subject after the to-address, or preceding the subject with '##' followed by '#' before the message.
Explanation: To ensure full compatibility across both MO (Mobile Originated) and MT (Mobile Terminated) messages, developers must support two specific formats for delimiting or indicating the subject field. These are: Enclosing the subject in round brackets () after specifying the to-address, and preceding the subject with '##' and then the subject, followed by '#' before the message content.