张宝义的回答：

I have been the League branch secretary in our class.

钟昌林的回答：

I have been the League branch secretary in our class.

懒得糊涂的回答：

league branch secretary这么说是没错的，或者你可以这么说： secretary of youth league committee 团支部书记

王若扬的回答：

团支书：student in charge of corps 我在班上一直担任团支书一职。i am always in charge of the corps in my class .