-- Shirley what were you doing at three o’clock yesterday? I was sitting by the window

问题补充：

-- Shirley, what were you doing at three o’clock yesterday?

-- I was sitting by the window, to the music.

A. listen

B. listening

C. listened

D. to listen

答案：

A. listen

(答案→)B. listening

C. listened

D. to listen

解析：本句的意思是“我正坐在窗户旁，听音乐。”根据句意可知，本处的“听”实际上与“坐”是同时的，因为前面有逗号，故应该用分词来表示伴随的情况。所以本题选B。