He is the only one of the students who come from the country.这句话里定语从句的先行词是什么?

此句为病句,正确表达应为：
He is the only one of the students who comes from the country.他是学生中唯一来自农村的.（先行词为the only one)
He is one of the students who come from the country.他是来自农村的学生之一.（先行词为the students)