1. But as proved by the biosphere experiment中as是关系代词,引导非限制性定语短语。
2.as此时的意思为“这件事”“这一点”,e.g.
He is late, as is often the case. 他迟到了,这是经常的事。
As is usual with children, they soon got tired. 孩子们一贯如此, 他们很快就厌倦了。
David, as you know, has not been well lately. 大卫最近身体不太好,这你是知道的。
3.此句中as的意思是Staying alvie will be a daily chanllenge这件事(求生是每日的挑战),as的作用是把这件事引导进了as proved by the biosphere experiment这个非限制性定语短语,由于proved by the biosphere experiment缺少is,不能构成is proved by the biosphere experiment这种完整定语从句,所以只能形成短语(功能类似独立主格)。
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