Final answer:
The correct action when a school bus is stopped at a railway crossing is to open the door to listen for approaching trains, ensuring the safety of all passengers through a thorough check.
Step-by-step explanation:
Once your school bus is stopped at a railway crossing, you must open the door to listen for approaching trains. This safety measure ensures that both visual and auditory checks are used to detect any incoming trains before crossing. It is important for the driver to pay close attention and use multiple senses to prevent accidents.