He seems very queer sometimes, and even Jennie has an inexplicable look. It strikes me occasionally, just as a scientific hypothesis,—that perhaps it is the paper!
I have watched John when he did not know I was looking, and come into the room suddenly on the most innocent excuses, and I’ve caught him several times LOOKING AT THE PAPER! And Jennie too. I caught Jennie with her hand on it once.

Why does the narrator believe that John and Jennie are looking at the wallpaper?
She thinks that the wallpaper is having the same effect on them as it is on her.
She thinks that they are planning to replace the wallpaper with a more pleasing pattern.
She thinks that they enjoy studying the images created by the pattern and the colors.
She thinks that they are attempting to figure out why the different colors bother her.