Answer:
A person who holds extreme beliefs is an extremist.
Explanation:
Among the three suffixes provided, the one that fits the description is the suffix -ist. This suffix is used to refer to a person who performs a certain action, or who has certain beliefs or principles. For instance, a person who specializes in an area is a specialist. A person who is an adept of communism is a communist. Having that in mind, we can easily add -ist to the root word "extreme". A person who holds extreme beliefs is an extremist.
