A、Because her lover is in prison. B、Because she lost her lover. C、Because she failed the history examination. D、Because she does

M: Hello, Mary. Why do you look so upset?
W: Well, every February, candy, flowers and gifts are everywhere. But where is mine? I hate this St. Valentine’s Day. Who on earth is this saint and why do we have to celebrate this holiday?
M: Oh, don’t be so depressed; your Mr. Right is waiting for you not far away. Just be a little patient. And I can tell you that the saint himself was not very happy on this day either.
W: Why? That’s interesting, tell me.
M: Well, there are several stories about this man from both Christian and ancient Roman traditions.
W: That means we are not very sure of the exact history of it, are we?
M: Yes, but we do know that February has long been a month of romance.
W: Then what happened to this Valentine? Why did you say it’s a tragedy?
M: Well, one story said that Valentine actually sent the first "valentine" greeting himself. When he was a prisoner, Valentine fell in love with a young girl who visited him during his confinement. Before his death, he wrote her a letter, in which he signed "From your Valentine".
W: Wow, it’s so sad and so romantic!
M: Well, so don’t be upset anymore. At least your future Valentine will be there and alive.
W: That doesn’t help. I’m still very frustrated.