And the exact contributions of man and nature to the changes taking place are surely unknown, even if it is accepted that man is making natural cycles more pronounced.

自然和人类对变化的确切影响，无疑是未知的，即使在公认人类对自然界循环的影响更加显著的情况下。

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But who's to say the trees they chew don't contain some unknown bacterium that stops sheep becoming man-eaters?

但谁又敢说它们咀嚼的树木中也会含有那种防止羊吃人的未知细菌呢？

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Husband: I Saw my wife with a unknown man going to movie!

丈夫：我看见一个不认识的男人正和我的妻子去看电影！

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Shortly before midnight on Saturday, 8 September, an unknown man thought to be in his 20s prepared for a terrifying journey.

BBC: Angolan plane fall man: Residents seek end to mystery

The unusual mummification of unknown man E, believed to be Pentawere, points to a "nonroyal burial" that includes use of goat skin to cover his body.

CNN: Study revisits mystery of Egyptian king's killing

Brian Polite said Wednesday that a trooper interviewed her around 4:30 a.m. that morning at the Thomas Edison service plaza in Woodbridge and took a report that an unknown man had thrown her to the floor of the bus and then onto the road.

WSJ: Woman sues Eagles' McCoy, claiming assault on bus