1.She’s a great woman.She raised 3 kids all by herself. She’s a great woman who raised 3 kids all by herself.2. That’s the person.I want to introduce him.That’s the person whom I want to introduce.That’s the person who I want to introduce.3. That’s the guy.His father is a millionaire.That’s the guy whose father is a millionaire.4. That’s a problem.It has no solution.That’s a problem which has no solution.