What text are you talking about ?Mark Twain had many books. Include a snippet of the text ,so I can answer the question.
Adverbial is the answer, just took the test
I would say D, as it would allow the reader to understand the comparison being made
The correct answer is A. reliable.
The writer was 'an authoritative source' because of her degrees, guest appearances, etc. Thus, she was a source you could rely on, she was reliable, given that she had experience to back her ideas up. Therefore A is the only correct answer.
