此句中用one,是an unforgetable moment 的同位语,I will always treasure是省略了关系代词that的定语从句.此句还可以是:Meetingmy uncle after all these years was an unforgetable moment,one that I always treasure.或:Meeting my uncle after all these years was an unforgetable moment,which (此处只能用which,不能用that,因为此是一个非限制性定语从句)I always treasure.或:Meeting my uncle after all these years was an unforgetable moment,and I always treasure it.
另外,treasure单词是否漏打了字母r?