Solid geometry has enabled astronomers to calculate the positions of the heavenly bodies relative to one another.
A、ontopofD
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The fear of smallpox, which terrorized the eighteenth century, has no analogy(likeness) today.
Communicationisoneofthemostimportantbondsthatholdculturalsystemstogether.
TheSalkvaccineisamajorfactorinthefighttoeradicatepolio.
Eyespots, the most rudimentary eyes, are found in protozoan原生动物 flagellates 鞭毛虫 , flatworms 扁形虫 , and segmented worms片段 蠕虫 .
Blue－greenalgaegrowabundantlyinsaltmarshes.
