聚精会神

例句：

1. 1. He sat there, engrossed in the book.
   他坐在那里，聚精会神地看书。
2. 2. She was so absorbed in her work that she didn't notice the time passing.
   她太专注于工作了，以至于没有注意到时间流逝。
3. 3. The teacher asked us to focus on the lesson and not get distracted by our phones.
   老师要求我们集中精力上课，不要被手机分心。