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铅笔是人们日常学习、工作中最常用的书写工具之一。当你随意拿起一只铅笔,细心的人就会发现铅笔上的一端总是印有「H」、「B」或「HB」不同的英文字母。这些标有不同英文字母的铅笔,究竟表示什么?知道的人并不多。
Pencil is one of the most commonly used writing tools in people’s daily study and work. When you feel free to pick up a pencil, attentive people will find that the end of the pencil is always printed with different English letters “H”, “B” or “HB”. What is the meaning of these pencils marked with different English letters? Not many people know.