The BCTA Road Safety and Traffic Rules Book tells every driver to 'buckle up' before moving off. What does it give as the reason?

1. A seat belt stops the airbag from deploying unnecessarily
2. A seat belt restrains occupants in a crash and is the best defence against serious injury
3. A seat belt is only needed above 50 km/h, where crash forces become dangerous
4. A seat belt is only needed by the driver, because passengers are cushioned by the seats