The sentence that uses parallel structures is B) My three favorite activities are writing, reading, and going to the library.
A parallel structure means that the same form of a verb is used in a sentence, and as you can see, here only gerunds are used - writing, reading, going - they all have -ing in the end.
The other sentences don't have a parallel structure because they don't use the same forms.
The underlined word <em>unique </em>is used as C. predicate adjective in the sentence.
A predicate adjective is the adjective following a copulating/linking verb.
The linking verb here is <em>is, </em>and the predicate adjective is therefore the adjective following it, which is <em>unique. </em>
A source that consists of original material, such as an interview
Georgia has worked there for 15 years