Which statement best expresses the theme of "the yellow wallpaper"?
a. john thinks his wife has gone insane at the end of the story.
b. the narrator comes to believe she is trapped in the wallpaper.
c. without the freedom to express themselves, people can become mentally ill.
d. a woman thinks there is someone trapped in the wallpaper and becomes very ill.

c. Without the freedom to express themselves, people can become mentally ill.

Explanation:

In the narrative Yellow Wallpaper, the wife finds herself trapped under the controlling supervision of her physician husband John, who does not take his wife´s grievances seriously. He considers her health state, a case which  only needs good rest, good air and good nourishment - a temporary nervous condition.

Her husbands control of her wishes forces her get more involved in the negative aspects of the yellow wallpaper thus affecting her self-estime and mental state.

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did you ever get an answer? i'm on the same question : (