How are voice and word choice connected to research?

Voice is the sound created by the writer and the perspective from which the piece is written; voice is created primarily through tone and point of view.  

Tone is the way the writing sounds to the reader.  Is it serious, flippant, sarcastic, reasoned, witty, humorous, casual, or some mixture of these elements? Academic writing, such as research papers or case studies, often calls for a reasoned or serious tone. Some refer to this as a formal voice. Tone is created, in part, through word choice, ordiction.

Word choice is inextricably connected to “ voice”: that which connects the reader to the text and establishes a relationship between the reader and the author

Diction, or word choice, supports the tone that a writer hopes to convey. Thus, for a formal style, use “made a mistake” rather than “screwed up.” Words marked in the dictionary as “slang” or “informal” would not be good candidates to include in a formal paper.  However, if you were writing a narrative, then such vocabulary might be appropriate.

The answer to your question is option a

An adverb clause is the answer?