lower chalk

例句：

1. 1.The teacher used lower chalk to write on the blackboard.
   老师用粉笔在黑板上写字。
2. 2.The children were playing with lower chalk in the classroom.
   孩子们在教室里用粉笔玩耍。
3. 3.Lower chalk is a common material for writing on whiteboards.
   粉笔是白板上常用的书写材料。