not until和过去完成时

not until:Not until she had lost her daughter and husband did she realize her true love。知道她失去了女儿和丈夫才发现她的真爱（她本来以为自己不爱她老公,等她老公走了 她发现自己是爱他的）你那个句子里的NOT 是跟 had连的,i hadn't understood the problem until he explained it。