The drivers of which vehicles, when stopping or parking on mountain roads, as well as on upgrades and downgrades, must use anti-rollback chocks?

• 1Trucks whose maximum permissible mass exceeds 3.5 tonnes.
• 2Of tractors.
• 3Of buses.
• 4Answers 1, 2, and 3.
• 5Answers 1 and 2.