The correct option is A Naive as she is
An adverb clause is a group of words containing a subject and a verb,
and it functions as an adverb, by modifying an adjective, verb or an
adverb. Adverb clauses generally begin with a subordinate conjunction
(since, because, while, etc.).
Option A is correct because it is an
adverb clause of concession or contrast, 'as' is a conjunction that refers to the contrast ideas: 'naive she is', 'earned her position'.
Option B is incorrect because it is coordinate or complete clause whereas an adverb clause is subordinate/dependent.
Option C is incorrect because it
is a phrase, not a clause.
Option D is incorrect because the answer lies in A.