VOA慢速英语2016.07.28
[audio]http://sound.yywz123.com/tingbbs/voa/voa20160728.mp3[/audio]_______________________________ . That claim could change theories about how life developed on our planet. The claim came from researchers at Brock University in Canada. They wanted to measure the levels of oxygen in the Earth\'s atmosphere nearly a billion years ago.研究人员发现，十亿年前，地球上氧气的含量，远超出科学家的预想。这一发现可能会对地球生物演变的理论产生变革。这一发现是由加拿大布鲁克大学的研究人员提出的。 _______________________________。
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