，memories of staying abroad as an exchange student flooded into his mind.
A. Listening to these songs
B. Having listened to these songs
C. He was listening to these songs
D. When he listened to these songs
网友回答
A. Listening to these songs
B. Having listened to these songs
C. He was listening to these songs
(答案→)D. When he listened to these songs
解析：考查句子结构：句意：当他听这些歌的时候，在国外做交换生的经历浮现在他的脑海。因为主语不一样，所以不能用非谓语作状语的用法，排除AB项，选C项的话，两个简单句中间没有连词，所以选D。