What may be the consequence of a long bus drive, when the tachometre indicator is constantly in the red field?

In the photo you can see a bus rev counter (tachometer) with a green and a red zone, and the needle is in the red zone. Driving for a long time in the red zone of the rev counter may damage the engine - answer B.

The Road Traffic Act prohibits a driver from using a vehicle in a way that causes nuisance from excessive exhaust emissions or excessive noise, and the vehicle must be maintained so that it does not endanger safety. The red zone is the engine speed range in which the engine works at the limit of its strength: the temperature and the forces acting on the pistons, connecting rods and bearings rise. Driving for a long time in this zone can end with the engine seizing or its parts cracking. It does not mean optimal fuel consumption (answer A) - the engine then burns the most fuel. Nor does it increase engine performance (answer C). You change up a gear before the needle enters the red zone.

Legal basis: Art. 60 para. 2 point 2 and Art. 66 para. 1 point 1 of the Road Traffic Act (Prawo o ruchu drogowym)