单选题

A To invite the student to attend a meeting with her.

B To let the student know that she will have to leave soon.

C To announce that she will be speaking at a meeting.

D To explain why she cannot help the student right now.

解析：
学生问辅导员现在忙不忙，辅导员对学生说“There’s a meeting at two-thirty, but I have a few minutes”，所以可知辅导员这么说是为了告诉学生之后还有一个会议要开，她过一会儿就要离开，所以本题选B。