Any vessel in need of carrying out deck washing must be（）by the department concerned beforehand.

A.rotor blades and landing gear
B.unloading of passengers
C.loading of cargo
D.pilot's visibility

A.Disease of Crew
B.Crew illness
C.Group illness
D.Mass disease

A.start the engine in cold weather
B.aid in helping personnel breathe
C.prime the sprinkler system
D.prime the air supply