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Lightning Helps Fertilize The Soil Our bodies need protein, and proteins contain nitrogen. The air we breathe has plenty of nitrogen to satisfy our needs. Butthat nitrogen is not available to us directly from the air. The only way we can get nitrogen
发表于:2018-12-31 / 阅读(52) / 评论(0)
英语听力文摘 English Digest
英语听力文摘 English Digest