What does this sign indicate?

• There is a hidden school bus stop ahead.
  Explanation:

  "This sign alerts drivers to the presence of a school bus stop that may be obscured by curves, hills, or other visibility issues. Drivers should reduce their speed, stay alert, and be prepared to stop if a school bus is present or children are crossing the road."
• There is a railway crossing on the road ahead.
• There is an intersection ahead.
• There is a school zone ahead.