C. Women in the 19th century often played a lesser role in marriage.
Explanation:
The theme refers to the subject matter or message of a piece of writing. In "The Yellow Wallpaper," the author Charlotte Perkins Gilman intends to direct attention to the role of women in the nineteenth century. In that respect, she questions the institution of marriage, and how women were only expected to get married, have children and submit to their husbands.
