Not the conclusion. The argument doesn't claim gender distinctions are arbitrary. It claims gender traits don't sort people into two non-overlapping groups, which is a different point. (A) is a stronger, separate claim about the legitimacy of gender categories that the author never makes.

Not the conclusion. The argument says gender is socially constructed but doesn't address when gender traits are determined. (B) might be a reasonable inference from the social-construction premise, but it isn't the main point. The author isn't arguing about timing; she's arguing that "sex" and "gender" refer to different things.

Not the conclusion. The author says people can have both masculine and feminine traits, but doesn't indicate whether those traits correlate with male or female sex.

This is the main conclusion. The argument opens with the context that the terms are often used interchangeably, pivots with "but," and proceeds to correct that practice by drawing a distinction between sex (biological) and gender (socially constructed). Sentences three and four are premises supporting the distinction. (D) restates the claim the author is defending.

Not the conclusion. The argument mentions that gender is socially constructed, but it doesn't claim society dictates "proper behavior" or contrast society's role with the individual's. (E) goes further than what the author actually says.