问题补充:
the days he had spent with his American friends, he couldn’t help.
A. Keeping up; smile
B. Staying up; smiling
C. Looking back on; smiling
D. Looking at; to smile
答案:
A. Keeping up; smile
B. Staying up; smiling
(答案→)C. Looking back on; smiling
D. Looking at; to smile
解析:考查非谓语动词,第一空考查现在分词作状语,用Looking back on回顾,第二空考查现在分词作宾语,can’t help doing情不自禁作某事,句意:回顾他与美国朋友在一起的那些日子,他情不自禁笑了。所以选C。