mark signal

例句：

1. 1. The teacher marked the important points on the blackboard.
   老师在黑板上标出了重要内容。
2. 2. Mark your place before you start reading.
   在你开始阅读之前，请做好标记。
3. 3. The carpenter marked the wood to make it stronger.
   木匠给木头做了标记，使其更坚固。