What is the mandatory legal requirement regarding passenger seatbelts on interurban buses in Chile under Ley 20.068?

1. Seatbelts are optional for all passengers
2. All interurban buses manufactured since 2008 must be equipped with seatbelts in all passenger seats, and their use is mandatory for every passenger throughout the journey
3. Seatbelts are required only for the driver
4. Seatbelts are mandatory only for passengers over 65 years old