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金属材料在生产生活中有广泛的用途,人类的生产生活离不开金属.
如图,在Rt△ABC中,∠ACB=90°,CD⊥AB于D,若AD=3,BD=8,则CD=____
As we know, his father is a very famous scientist in physics. But what you don't know is that he _______ as a farmer for five years.
有关我国国情的叙述,不正确的是( )