How does the fact that night is a memoir rather than a biography or informational text the author achieve his purpose in this excerpt?
the author is able to present an objective account of the situation.
the author is able to personalize the event by using the words we and us.
the author is able to give only the facts so that the reader understands the situation.
the author is able to rely on the denotative meanings of words to tell about the event.

The author is able to personalize the event by using the words we and us.

Explanation:

One of the advantages of Night is that the text is a memoir rather than a biography or an informational text. This allows the author to achieve things that would be impossible with a different type of text. For example, the author is able to personalize the event by using the words we and us. Moreover, because this is a personal account, the author does not need to be objective. Instead, he is able to tell us about his life in the way in which he experienced it.

quite an interesting way to teach topic sentences, because the answer to this question is the best definition of a topic sentence that one can present, it is as if answering the questions taught you how to do it, this is some real teaching, it is terribly well-done.

the topic sentence in this paragraph is:

topic sentences writers stay on track and keep a paragraph from becoming an aimless collection of sentences about an idea.

which incidentally tells you what a topic sentence should be.