Answer: Option C
Messenger : a person who carries a message or is employed to carry messages.
Steward : a person employed to look after the passengers on a ship, aircraft, or train.
Forerunner : a person or thing that precedes the coming or development of someone or something else.
Pilot : a person who operates the flying controls of an aircraft.
Harbinger : a forerunner of something.
Synonym of Harbinger is Messenger