a post office I stopped some stamps.　A. Passed buyingB. Passing to buy　C. Having pass

问题补充：

a post office, I stopped some stamps.

A. Passed, buying

B. Passing, to buy

C. Having passed, buy

D. Pass, to buy

答案：

A. Passed, buying

(答案→)B. Passing, to buy

C. Having passed, buy

D. Pass, to buy

解析：考查非谓语动词。第一空，主语I与pass之间是主谓关系，故用现在分词，在这作状语，第二空，stop to do 停下来去做另一件事，stop doing停止正在做的事，句意：通过邮局，我停下来买了一些邮票。所以选B。