Which of the following actions should be performed prior to changing a wheel on a bus?

The question is about the action you start with when changing a wheel on a bus. You put chocks under the opposite wheel - answer A.

The Road Traffic Act requires you, when the vehicle is parked, to secure it and to take the precautions necessary to avoid an accident. A bus raised on a jack may move, and then it falls off the jack onto the person working at the wheel - chocks under the wheel on the opposite side keep it in place. You do not release the parking brake (answer B), because it is what holds the bus - in many buses it works only on one axle, which is why the chocks are an additional safeguard. Putting the gear lever in neutral (answer C) does not secure the vehicle, and in fact takes away the extra resistance of the engine. Before changing the wheel, you also turn on the hazard warning lights.

Legal basis: Art. 46 para. 5 of the Road Traffic Act (Prawo o ruchu drogowym)