The correct option is C Plagiarist
Pluralist is a person who supports a system in which two or more states, groups, principles, sources of authority, etc., coexist.
Imitator means someone who copies the behaviour or actions of another.
Plagiarist means one who copies from other writers.
Copycat is a person who copies another's behaviour, dress or ideas.
So, ''Plagiarist'' is the correct option.