A person who speaks or supports an idea
A. Pioneer
B. Adviser
C. Advocate
D. Ideologist
Answer: Option C
Solution (By Examveda Team)
One word substitute is Advocate.Pioneer: a person who is among the first to explore or settle a new country or area.
Adviser: a person who gives advice in a particular field.
Advocate: a person who publicly supports or recommends a particular cause or policy.
Ideologist: someone who develops or supports a particular ideology.

Join The Discussion