一项新研究指出人类朋友聚散有日，但马如得到友善对待，就会成为你最忠实的老朋友。

Human friends may come and go, but a horse could be one of your most loyal, long-term buddies if you treat it right, suggests a new study.

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啊！良心！良心！人类最忠实的朋友。

Ah! Conscience! Conscience! Man's most loyal friend.

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但是书籍是人类最忠实的朋友，是人类进步的阶梯。

However, books are faithful friends of mankind and steps to human progress.

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