Which quotation from Flatland most effectively illustrates the claim?

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Flatland is an 1884 novel by Edwin A. Abbott. The narrator describes the novel's setting as a world consisting entirely of two-dimensional geometric figures, whose existence is confined to the surface of a plane:

"As early as the eleventh century of our era, triangular houses were universally forbidden by Law, the only exceptions being fortifications, [gun]powder magazines, barracks, and other state buildings, which is not desirable that the general public should approach."

"Every human being in Flatland is a Regular Figure, that is to say of regular Construction. By this I mean that a Woman must not only be a line, but a straight line; that an Artisan or Soldier must have two of his sides equal."

"Imagine a vast sheet of paper on which straight Lines, Triangles, Squares, Pentagons, Hexagons, and other figures, instead of remaining fixed in their places, move freely about, on or in the surface, but without the power of rising above or sinking below it...and you will then have a pretty correct notion of my country."

"I call our world Flatland, not because we call it so, but to make its nature clearer to you, my happy readers, who are privileged to live in Space."