摘要
Many of us still call pencils lead pencils. But we are really badly out of date. Most people stopped using pencils filled with lead about four hundred years ago! Lead is a soft, heavy metal. It makes a grey mark if you rub it on a piece of paper. About the year 1300, men were using
出处
《中国远程教育》
1984年第4期60-61,共2页
Chinese Journal of Distance Education
