题干分析：对话目的。

原文定位：

A: Okay. Well, you know, it's time to officially declare your major field of study. Have you given it some thoughts?

S: Yeah, lots. But here's the thing, I love all my history courses, but after I graduate from here, I'd really like to be a social worker, and I'm not sure history's the best preparation for that.

选项分析：学术顾问向学生提到是时候正式选主修专业了，问学生考虑过没有，学生回答考虑了很久，但是还没有决定，可知应选B选项。A、C、D选项未提及。