15.(A). People in the hall were surprisingly relaxed.

　　(B). The hall had a strange odor.

　　(C). Someone found a few cents in the hall.

　　(D). The lecturer tried to calm the rowdy students.

　　16.(A). Professor Stone doesn’t plan to retire for years.

　　(B).Every year Professor Stone talks about retiring.

　　(C). Each year Professor Stone retreads his tires.

　　(D). Professor Stone has been threatened many times.

　　答案与音频文本：

　　A B

　　15. There was an unexpected sense of calm in the lecture hall.

　　16. Year after year, Professor Stone threatens to retire.