Which of the following guidelines should you adhere to when setting up a landing zone for a​ helicopter?
A.Mark each corner of the landing​ zone, and put a fifth warning device on the downwind side of the landing zone.
B.Make sure the landing zone is 50 to 75 feet from any crashed vehicles if the helicopter is landing at the scene.
C.Keep spectators 50 to 100 feet from the landing zone.
D.Select an area that is a flat square with​ 100-foot sides for a small helicopter.