再加上钙，镁起着牙齿和骨骼硬度不可或缺的作用。
Together with calcium, magnesium plays an integral role in tooth and bone hardness.
它在篇章组织，联系观众方面起着不可或缺的作用。
It plays a vital role in organizing the discourse and engaging the audience.
社区与学校、家庭一样，对幼儿教育发挥着不可或缺的作用。
Communities as well as kindergartens and families play an essential role in the educational for children.
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