“The man we know who is a work”这句话有问题吧 主语是“the man”,“we know ”是定语从句修饰主语“the man”的（此处that省略了）,“who is a worker”肯定不能做谓语,所以句中缺少谓语,应该去掉who,is系动词做谓语.后面这句主语是“we”,谓语是know ,宾语是the man,who is a worker是定语从句修饰宾语,所以是对的.此类问题首先要分析句子结构,看句子是否完整,然后再根据句意来看是否有问题.