Question: What type of data services support user-initiated service level up- and downgrading in A/Gb mode and GERAN Iu mode?
Option 1: Non-transparent multislot data services
Option 2: Transparent multislot data services
Option 3: Single-slot data services
Option 4: Circuit-switched data services
Explanation: User-initiated service level up- and downgrading is specifically applicable to non-transparent multislot data services, allowing users to request changes to the maximum number of traffic channels and/or wanted air interface user rate parameters.