What can cause the air compressor in a braking system with a multi-circuit safety valve to deliver compressed air continuously?

The selected combination is correct because both choices address critical issues that can lead to continuous air delivery from the compressor.

1. When the piston wear in the air compressor is significant enough, it fails to reach the cut-off pressure, meaning the compressor does not stop working even when adequate pressure is generated. This is a safety concern as it indicates the compressor may need maintenance or replacement to ensure proper braking function.

2. A leak in a compressed air circuit connected to the multi-circuit safety valve means that air is lost, requiring the compressor to work continuously to maintain the necessary pressure for safe braking. This situation could also compromise braking performance, which is crucial in adhering to German traffic regulations that demand vehicle safety and reliability.

Understanding these factors is essential for maintaining effective braking systems as stipulated by the relevant safety regulations in German law, ensuring that vehicles are capable of safe operation on the road.