Stones...
A landlord is threatening to evict a father and his young daughter, unless she agrees to marry him. In a false gesture of sincerity, he offers her an opportunity for them both to remain in the house, without marrying him. He has a silk bag in which he says he has placed a white and a black stone from the footpath on which they're standing. If she picks the white stone from the bag, without looking, she wins; if she picks the black stone, she loses. However, the young girl saw him place two black stones in the bag. She can't expose him in front of witnesses without angering him and making things worse. How does the girl win?

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