For anyone still looking for this questions answer, or for anyone looking to confirm it, I'll put this here.
- The vivid description of the landscape.
- The first-person point of view.
A vivid description of any nature is a common trait of a memoir. Because memoirs are a collection of memories from the authors real life, they are able to recount such events in more detail than someone who has just made the story up.
The vast majority of memoirs are written in past tense with a first-person point of view. This is because they are recalling real events that happened to them sometime in their past. Although not all memoirs do this, that is still the correct answer because most do, and Shackleton does. Shackleton's "South!" is written in first-person.
The other options do not apply here.
There is no "imagination" in memoirs, because memoirs are factual events (or at least said to be/supposed to be) That means the first two are out.
Third-person point of view is also out, because as I stated above, Shackleton's "South!" is written in first-person.
