One of the most popular tools for ephemeral writing is the pencil. Pencil marks, unlike those made by writing implements using fluids, can be easily erased. Although commonly called lead pencils, they do not contain any of that metal but are composed of a mixture of graphite (a form of carbon) and clay.
- mark [mɑ:k] n. (笔)迹，痕迹
- erase [iˈreiz] v. 擦掉
- lead [led] n. 铅
- graphite [ˈɡræfait] n. 石墨
- clay [klei] n.黏土
