用英文翻译：最后他们两个人都回到了各自的教室

Finally,they both went back to their own classroom.

Finally,both of them went back to their own classroom.

Both of them went back to their each classroom at last.
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At last,they two went back to the classroom of their own.

At last, each of them went back to his own classrorm.

20.也许蓝色的天上有他们各自想念的对象，贵树回到了东京念大学 21.还是那个1 do you know，桂树san ?the speed of cherry blossoms falling is

At the end, they got back to each classroom

In the end, both of them returned to their own classrooms.

Eventually, both of them went back（returned) to their own classrooms.（classroom一定要用复数，因为是各自的教室，所以应该有两间）

Finally, they both went back to their respective classroom separately.
classroom要用单数，因为各自的教室每人只有一个。

At last they both went back to their own classroom

Finally they both return to their classrooms