问题
选择题
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
答案：A
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。