What does a triangular warning sign with two curved black arrows in an S-shape curving first to the right indicate ('Dvostruka krivina, od kojih je prva udesno')?

1. Double curve or series of dangerous curves ahead, the first to the right (Dvostruka krivina od kojih je prva udesno)
2. Sharp 90-degree right turn only
3. Road splits into two separate carriageways
4. Traffic roundabout 500 metres ahead