one of ,the one of 后谓语单复数的区分

这个谓语都应该是单数.
但是,当这两个充当定语从句先行词时,前者先行词是one of 后的名词；后者先行词是the one.
所以,前者的定语从句(引导词充当主语时）谓语用复数；后者的定语从句（引导词充当主语时）用单数.
例：
  He was one of the boys who were late.他是迟到男孩中的一个（不止一个男孩迟到）
  He was the one of the boys who was late.他是男孩中迟到的那个（只有一个男孩迟到）