The correct option is D Cosmopolitan
A person who regards the whole world as his country is Option C, Cosmopolitan. Option A, Patriot is a person who loves his country and is proud of it. Option B, Nationalist is a person who strongly believes that his country is better than others.. Option D, Metropolitan means belonging to a large busy city. Thus, options A, B and D are incorrect and the correct word for the phrase is Option C, Cosmopolitan.