A、White. B、Yellow. C、Red. D、Green. D推理判断题。原文中提到四种颜色white，brown，green，red，根据原文Dentist’s offices are beingrepainted in brown，green

People need to go to the dentist’s office to solve their tooth problem, but most of them would rather endure pain than going there. The reason is quite simple — they are scared. You wait in a white waiting room. All is silent until an assistant calls your name and leads you back to another white room, which is filled with machines and frightens you still further.
    At the Medical College of Georgia, dentists are taught principles that should help reduce the patient’s anxiety and tension. Assistants and receptionists are taught to smile and speak to the patients. This helps create an atmosphere of trust. Dentists themselves are being taught to communicate more fully with the patients. A phrase such as you’re doing fine tells the patient that the dentist is aware of the patient’s situation. These phrases also help by rewarding the tolerance of pain. Dentist’s offices are being repainted in brown, green, and other relieving colors. Red should be avoided at all costs, because it brings to mind blood and pain. Paintings and other distractions are placed in the room; music is played to help the patients ignore his or her pain.
    Some dentists go much further. They take an active role in teaching their patients to relax; some are teaching their patients deep muscle relaxation and breathing control. Some use advanced techniques to help their patients relax in the chair.
Questions:
30. Why are most people unwilling to see the dentist?
31. What is the color suitable to use in painting the wall in a dentist’s office?
32. What is the main idea of the passage?