Mary Allen was my best friend—like a sister I never had.We did everything together: piano lessons，movies，swimming and horseback riding. When I was 13，my family moved away.Mary and I kept in touch through letters and we saw each other on special occasions(场合)—like my wedding and Mary’s.Soon we were busy with children and moving to new homes，and we wrote less often.One day a card that I sent came back stamped “Address Unknown”.

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