<span>e. b and c only
As long as a speaker lets the audience know who the author of a study is, and gives a brief overview of their credentials or qualifications, the audience should be able to trust the information that the speaker is presenting, based on their credible research.</span>
It suggests the narrator is traveled without thinking of the time.
This one makes the most sense because he says "at length, I found myself" some traveled for a while. "As the shades of the evening drew on" supports that he was traveling without hinting of the time because night draws on unexpectedly.
