If indutrial pollution continues to deplete the ozone layer, the resulting increase in ultraviolet radiation will endanger human health, causing a rise in the indidence of skin cancer and eye disease, ( and perhaps even threatenting) global ecological systems. B) and may even threaten 问： 为什么不是 threat, 为啥要用过去分词？
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发表于 2003-5-8 18:32:00
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