sit in on a class

I was fortunate to sit in on a graduate class taught by Dave Hanson that used this as the text.

我很幸运，读研究生的时候，Dave Hanson就拿这本书当教材给我们上课。

互联网摘选

It is possible that a student in the United States can "sit in" on a class at a university in China.

美国的学生可以“坐”在中国某一大学的课堂内。

互联网摘选

If you must sit in on a smaller seminar class, it's important to show up consistently starting with the first session, instead of halfway through the semester.

如果你一定要蹭人少的课，那么最好第一节课就出现在教室，并且保持高出勤率。

互联网摘选