someone made it是定语从句,修饰problem.从句前省略了关系代词that或which.那句子的主体是不是少了主语，定语从句中it指代什么？这句是少了成分。正确的说法有两种可能：（1）It wasn't the problem someone made it.（这不是某人制造的问题。）在这种情况下，it是主语，wasn't 是系动词作谓语，the problem是表语。someone made it是定语从句，修饰the problem。（2）Wasn't the problem the one someone made it.（难道这个问题不是某人制造的问题吗？）在这种情况下，the problem是主语，wasn't 是系动词作谓语，the one是表语。someone made it是定语从句，修饰the one。