单选题My father walked _____&nb

问题补充：

单选题Myfatherwalked_____intheroom,lookingasifhewasthinkingoversomething.A.now and thenB.up and downC.again and againD.over and over

答案：

B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”。