Ethos is used in this sentence. Speakers appeal to ethos to show that they are credible and trustworthy. Appeals to ethos emphasize shared values between the speaker and the audience. Speakers build ethos by explaining their credentials or background to show that they are knowledgeable or qualified to speak on a subject.
In this sentence, ethos is used because credibility is established by referring to the professor at Harvard—who has a PhD— whom the speaker consulted.
Your answer should be letter C) Expansive.
Some other synonyms are spacious or roomy!
Please post the excerpt next time.
1. Red Sea - refers to the parting of the Red sea, in the Bible. (<em>division</em>)
2. Ivory tower - allusion to a sheltered isolation. <em>(away from ordinary life</em>)
3. Siren and a harpy - refer to mythical creatures. (<em>dangerous creatures)</em>
4. The sword of Damocles- refers to an acient moral parable. (<em>something bad seems very likely to happen to you)</em>
5. Cold war - reference to the relationship between US and Soviet Union after WW II <em>(unfriendliness without fight, but with threats</em>)
6. Achilles's heel - reference to the mythological hero. (<em>a weak point in a person)</em>
7. Bart Simpson - allusion to the sitcom The Simpsons ( <em>mischievous boy</em>)
I believe the reader is experiencing A. suspension or disbelief.