请根据下面短文回答第下列各题： Old Mr. Green has lived in southern Iowa for a very long ti

me. He has worked on the land all his life and he sees no reason to stop now. His legs have bothered him for many years, and his hands have pain(疼痛). His wife has been asking him to get some help from a doctor, but he has never listened to her. He has known old doctor since he was a boy, so of course he trusts (信任)him. But its one thing to trust a doctor, another to really go and see him. At last, when he cannot work because of the pain, he has to let his wife take him to see the old doctor. "How long have you had problems with your legs, Mr. Green？""For three years!” "And your hands？ Theyve given you pain for a few years, right？ I think you might have arthritis (关节炎). I know youve been taking care of your farm by yourself all these years. From now on youd better get someone to help you on the farm and keep yourself warm. Come and see me again in two months. " Mr. Green feels sorry that he didnt come to see the doctor earlier. Mr. Green is a ______

A.teacher

B.farmer

C.doctor