第 74 课: 数学运算-5

He is making a line with a ruler. 他在用尺画一条线。

He is erasing the line with an eraser. 他用橡皮把线擦掉。

He is writing. 他在写字。

He is erasing what he wrote on the blackboard. 他把他写在黑板上的字擦掉。

Someone is writing on the blackboard. 有人在黑板上写字。

Someone is erasing the blackboard. 有人在擦黑板。

Someone is drawing on the blackboard. 有人在黑板上画画。

Someone is drawing on paper. 有人在纸上画画。