He is writing on the blackboard
黑板───blackboard;写字───write
The menu was on a blackboard.───菜单在黑板上。
On a blackboard, he drew five concentric circles.───他在黑板上画出五个同心圆。
He chalked the message on the blackboard.───他用粉笔把这条消息写在黑板上。
One of us held a paper nose in our hand, walked toward the blackboard with our eyes covered, and tried to put the nose into the head.───就是黑板上画好一个人头,蒙着眼睛,手上拿着一个纸做的鼻子,贴到人头上。
After a long time, the sky is just a word did not approach statistical big blackboard.───过了半天,天空简直成了字数没有办法统计的大黑板。
He began to work a problem on a "blackboard" with a piece of chalk.───他开始用粉笔在一块“黑板”上算题。