In what situations must you stop before crossing any railroad track?

• When a flagman is giving a signal to stop
• When a train is approaching so closely as to create an immediate hazard
• When an approaching train gives a warning signal of its speed or nearness to the crossing
• All of the above
  Explanation:

  "You must always stop before any railroad crossing when any of the following apply: 1. A flagman is giving a signal. 2. A train is approaching so closely as to create an immediate hazard. 3. A train gives a warning signal and is an immediate hazard due to its speed or nearness to the crossing. "