A、It made people happier. B、It did more harm than good. C、It increased risks. D、It made people sick. B演讲人在介绍完自己的职业后，用转折句对过去十年的工作

I am a health psychologist, and my work is to help people be happier and healthier. But I’m afraid that something I’ve been teaching about stress for the last 10 years is doing more harm than good. For years I’ve been telling people, stress makes you sick. It increases the risk of everything from the common cold to heart disease. Basically, I’ve turned stress into the enemy. But I have changed my mind about stress, and today, I want to change yours.
    Let me start with the study that made me rethink my approach to stress. This study tracked 30,000 adults in the United States for eight years.     Researchers found that people who experienced a lot of stress and believed stress was harmful in the previous years had a 43 percent increased risk of dying. But people who experienced a lot of stress but did not view stress as harmful had the lowest risk of dying of anyone in the study, including people who had relatively little stress. The researchers estimated that over the eight years 182.000 Americans died too young, not from stress, but from the belief that stress is bad for you. Now, if that estimate is correct, that would make believing stress is bad for you the 15th largest cause of death in the United States last year, killing more people than skin cancer and AIDS.
    You can see why this study freaked me out. Here I’ve been spending so much energy telling people stress is bad for their health. So this study got me wondering: Can changing how you think about stress make you healthier? And here the science says yes. When you change your mind about stress, you can change your body’s response to stress.
    What if you viewed stress instead as signs that your body was energized, was preparing you to meet this challenge? Now that is exactly what participants were told in a study conducted at Harvard University. Before they went through a social test, they were taught to rethink their stress response as helpful. That pounding heart is preparing you for action. If you’re breathing faster, it’s no problem. It’s getting more oxygen to your brain. Guess how was the result? Well, they were less stressed out, less anxious, more confident, but the most fascinating finding to me was how their physical stress response changed.
    So my goal as a health psychologist has changed. I no longer want to get rid of your stress. I want to make you better at stress. And we just did a little intervention. When you view stress in that way, your body believes you, and your stress response becomes healthier.
16.What does  the speaker say  about his  last 10 years’ teaching?
17.What do we know about death of the 182,000 Americans according to the researchers?
18.What did the Harvard researchers teach the participants before the social test?
19.What change has happened to the speaker’s goal?