If a Scheduled Plane Can't Fly Due to Maintenance Issues

If a scheduled plane can't fly due to maintenance issues, an airline's first response is likely to

A) Bring in its waiting back-up plane
B) Try to find another airline to fly the passengers
C) Try to find an LRU to fix the problem
D) Reschedule the flight for the next day and hope the plane works tomorrow
E) Cancel the flight and tell the passengers to find their own way out of town