My father walked in the room, looking as if he was thinking over something.
A. now and then
B. up and down
C. again and again
D. over and over
网友回答
A. now and then
(答案→)B. up and down
C. again and again
D. over and over
解析：now and then表示时间；again and again和over and over表示次数。这三个短语都不符合语境。walk up and down in the room意思是“在房间里踱来踱去”。