Many young people don't work hard, and regret it later when the opportunity is gone.They o

Many young people don't work hard, and regret it later when the opportunity is gone.They only realize it it is too late.
A. when　
B. before
C. in case　
D. until

(答案→)A. when　B. beforeC. in case　D. until解析：考查状语从句。句意：很多年轻人不努力，当机会失去的时候才后悔。他们认识到这一点的时候已经太迟了。when意为”当……的时候”，根据句意可知，选A。

回答的不错