Which statement correctly separates D1 from both B and D on passenger count?

1. D1 is any bus a category B driver may use if a conductor is on board
2. D1 begins at 8 passengers besides the driver and D begins at 8 metres regardless of seats
3. D1 is more than 8 and fewer than 17 passengers besides the driver; D is more than 16 passengers besides the driver or a bus longer than 8 metres
4. D1 is for standing city buses and D is for seated autocars only