A bus is driven outside a built-up area by a driver whose driving experience is under two years. What speed limit applies, and what must the bus display?

1. 100 km/h, with no additional marking
2. 90 km/h, with the 'Автопоезд' identification sign
3. 70 km/h, with the 'Ограничение скорости' identification sign on the rear left
4. 60 km/h, with the 'Колонна' identification sign