题目内容：

Some people won't realize the importance of their health _____ they have lost it
A、after B、when C、until D、unless
这道题选c,为什么不选D,请详细分析,谢谢
我觉得用unless翻译这句话也可以，为什么要用until

优质解答

not ···until意思是直到······才······时间状语引导词,这一点和汉语表达习惯不同.
有些人直到失去健康才意识到它的重要.
二者用途是不一样的
unless 除非···,如果不 ,是条件状语引导词,if ```not
I shall go tomorrow unless it rains. 　我要去,除非明天下雨
　------Shall Tom go and play football? 　　------Not unless he has finished his homework. 　
I won’t attend his birthday party unless invited (= unless I am invited)