What actions must an air traffic controller take upon recognizing a two-way radio communications failure, including a Mode A Code 7600 indication?

1. Test whether the aircraft can receive by requesting an observable maneuver or specified surveillance signal, transmit necessary information blind, use visual signals when applicable, and protect traffic using the route, level, and timing assumptions in the current published procedure.
2. Cancel the aircraft's flight plan and send military fighters to shoot it down.
3. Assume the aircraft has crashed and terminate all search efforts.
4. Change all runway numbers immediately.