Question: In RNSAP signalling, if an Information Element (IE) has a presence field value of 'mandatory' in its object set definition, how many times must it appear in a RNSAP message?
Option 1: Exactly once or more
Option 2: At most once
Option 3: Exactly once
Option 4: Zero or more times
Explanation: According to RNSAP definition rules, a 'mandatory' Information Element must appear exactly once in a constructed RNSAP message to avoid errors, ensuring consistency and correctness in message construction.