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. 。 keep them warm 6.聽(tīng)錄音填空(課文第三,四兩段) Nowadays, people do not use fire to _________or _________. In factories, workers use it ______melt metals. Metals are melted ________they can be made _______ different shapes. Factory workers also use fire to ________. Have you ever seen workers _______glass? They make bottles and vases __