在黑板上用on：on the blackboard：在黑板上;写在黑板上

例句：If you write on the blackboard, rub it off at the end of the lesson.

如果你在黑板上写字，下课时要擦掉。

相关介绍

blackboard：n.黑板，复数： blackboards

例句：

With a stick of chalk he wrote her order on a blackboard.

他用一截粉笔将她的指示写在黑板上。

On a blackboard, he drew five concentric circles.

他在黑板上画了5个同心圆。

There was a blackboard with seven names chalked on it.

黑板上用粉笔写着7个人名。

He chalked the message on the blackboard

他用粉笔将消息写在黑板上。