Replacing some things in your house at the right time can make you healthier. Some researches show us when and why the following things should be replaced.
Word Box: wool羊毛 dry-clean 干洗 bacteria 细菌
在1:800000的地图上,甲、乙两地的直线距离为8厘米,两地的实地距离是( )
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下列关于人体的生命活动叙述,正确的是( )