You can’t plain about being left out you don’t make any effort to share your joys and sorrows with others.
A. once
B. unless
C. when
D. though
网友回答
A. once
B. unless
(答案→)C. when
D. though
解析：句意：既然你没有努力的和别人分享快乐和悲伤，你就不要抱怨被别人遗忘。A. once 一旦， B. unless除非，C. when当…时候，既然，D. though虽然，所以选C。