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在南极上空看,甲机沿南极圈作逆时针方向飞行;在北极上空看,乙机沿北极圈作顺时针方向飞行,这两架飞机的飞行方向( )
下列自然现象中,可以用“扩散”解释的是( )
-- What will a science museum be like if you are asked to build one? -- I hope it will like a book.