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用一根蜡烛,你可制成一个可以在很长时间内能够自己上上下下的跷跷板。制作材料:一根长蜡烛,一根长铁钉,两只酒杯,两个小碟。
With a candle, you can make a seesaw that can lift itself up and down for a long time. Production materials: a long candle, a long nails, two glasses, two small dishes.