详解
Choice A is the best answer. The previous question asks which activity Smith argues it is possible for women to engage in. The answer, that she argues that women can act according to humanitarian principles while preserving their femininity, is best supported in the last sentence of the second paragraph: "must woman necessarily be less gentle because her heart is open to the claims of humanity, or less modest because she feels for the degradation of her enslaved sisters, and would stretch forth her hand for their rescue?" The leading tone of this rhetorical question makes it clear that Smith would answer it with a "no." In other words, Smith believes that women can uphold humanitarian principles while maintaining conventional feminine virtues.
Choices B, C, and D are incorrect because the cited lines don't support the answer to the previous question. Instead, they link women's conventional domestic concerns with the losses that would be incurred by a war over slavery (choice B), affirm that the potential horrors of war are enough to stir women out of a state of political inactivity (choice C), and equate women's patriotism with that of male political leaders (choice D).