a blackboard eraser的用法和样例：
- Trying to fix the tie , he took a blackboard eraser and hammered a large tack through his tie into his chest.
- Have you seen the chalk and the blackboard eraser?
- The room was furnished with some old tables, a blackboard, and an old stove.
- Andy chalks the alphabet on a blackboard.
- Just then,he saw a blackboard in front of him.