class field tower

例句：

1. 1. The teacher is giving a class on the history of the United States.
   老师正在给学生们上美国历史的课。
2. 2. She has been in the same class for three years.
   她在同一个班级已经三年了。
3. 3. The students are divided into different classes based on their abilities.
   学生们根据能力被分成不同的班级。