VANGUARD :

Answer: Option D

Race driver : someone who drives racing cars at high speeds.
Officer : a person holding a position of authority, especially one with a commission, in the armed services, the mercantile marine, or on a passenger ship.
Flag bearer : One who carries a flag, especially at a ceremony.
Pioneer : a person who is among the first to research and develop a new area of knowledge or activity.
Vanguard : a group of people leading the way in new developments or ideas.


Synonym of Vanguard is Flag bearer