Final answer:
A train crew should inform passengers about delays to ensure transparency and maintain trust. This shows respect for passenger's time and instills trust in the services provided.
Step-by-step explanation:
The most important reason for a train crew to announce the cause and probable duration of a stall to passengers is to ensure transparency and maintain trust with passengers. When dealing with unexpected delays or issues, providing clear and accurate information to the affected individuals can help manage their expectations and reduce frustration. Such communication also helps to build trust between the service provider and its customers, as it demonstrates a commitment to keeping passengers informed and shows respect for their time and plans.