They（ ）nod to each other when they met, and now and then they

They（ ）nod to each other when they met, and now and then they ( ) exchange a word or two.
A、would, used to
B、would, would
C、used to, used to
D、used to, would
【正确答案】：D
【题目解析】：used to do sth. 过去常常做某事，would有意愿做某事，句子含义是过去他们见面时会打打招呼，时不时还会交谈几句。