When were the first mechanical floor cleaners, which later became vacuum cleaners, invented?
第一台机械地板清洁机，后来变成真空吸尘器的机器是什么时候发明的？
| 单词 | mechanical floor |
| 例句 |
原声例句
6 Minute English 六分钟英语 When were the first mechanical floor cleaners, which later became vacuum cleaners, invented? 第一台机械地板清洁机，后来变成真空吸尘器的机器是什么时候发明的？ 6 Minute English 六分钟英语 Earlier I asked you: When were the first mechanical floor cleaners invented? 第一台机械地板清洁机是什么时候发明的？ 切达科学解读 In 2019, The Department of City Planning passed a bill for residential towers requiring mechanical floors higher than 30 feet to count towards the total zoning floor area. 2019 年，城市规划部通过了一项住宅楼法案，要求机械楼层高于 30 英尺才能计入总分区建筑面积。 |
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