Final answer:
At a railroad crossing with a ringing bell and flashing red lights, stop and wait until the train has passed and the signals cease before proceeding.
Step-by-step explanation:
When approaching a railroad crossing signal with a bell ringing and red lights flashing, the correct action to take is to stop your vehicle. Do not try to cross the tracks until the train has passed and the signals have stopped. It is important to ensure that there is enough space for your car to clear the tracks so you don't get trapped on them. Remaining stopped and stationary protects not only your safety but also the safety of passengers and other road users.