You always have to sit in the same room for three hours for multiple classes.

你必须在同一个房间为了多个课程坐三个小时。

youdao

Will they permit you to sit in on a few classes as an observer?

他们会允许你旁听几节课吗？

《柯林斯英汉双解大词典》

Sit in on two or three classes.

听两到三门课。

youdao

Sit in on two or three classes.

听两到三门课。

youdao