Answer: Elements that make "Walden" a memoir:
<u><em>- It is told from a first-person point of view.</em></u>
<u><em>- It focuses on an important experience.</em></u>
<u><em>- It provides information about the author's life.</em></u>
Explanation:
Henry David Thoreau's "Walden" is a memoir, because it's about his very <em><u>personal experience of living close to nature</u></em>, <em><u>leading a simple lifestyle</u></em> in the cabin he built and <em><u>his reflections</u></em> on this experience.
It's an account of <em>t</em><em><u>he author's personal point of view</u></em> and it's told from <u>a first-person point of view. </u>
The other explanations do not match the definition of a memoir, because <em>taking place over a short period of time does not necessarily make it a memoir</em> (so could a novel or a short story), <em>containing primarily transcendental ideas does not make it a memoir (</em>so could other types of text as well) and <em>emphasizing studying nature </em>doesn't mean it's personal (so could a descriptive text).