I felt somewhat disappointed and was about to leave,___ something_其他解答

I felt somewhat disappointed and was about to leave,___ something occurred attracted my attention.
[A] unless [B] until [C] when [D] while
为什么选C?请翻译句子

人气：314 ℃　时间：2020-04-19 18:10:23

解答

when表同时.
译：当我觉得失望,正要离开的时候,有东西出现了,吸引了我的注意力.