When I was in the second grade, one time at a gathering at our house, a teenage boy asked another one if they were a girl. When the girl responded yes, the boy asked that she prove it. Everyone snickered although I didn't quite understand the punchline. When I went back to school I tried the joke on a girl in class. The first one just brushed me off. The second one, Liz, held her face in her hands and pretended to cry. I told her that did not prove it. I'm not sure what response I would have found acceptable.
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