听力原文：M: Now, Miss Christina, I see that you are quite a heavy smoker. You told me you smoke about thirty a day. Well, my advice is quite simple: stop smoking. You know that cigarettes cause cancer and heart disease. Have you tried to give up? W: Yes, lots of times. But I just find it impossible to stop. M: Well, in that case, let me suggest five things which you can do. First of all, if you smoke strong cigarettes, you should change to milder ones. But that won't help you if you smoke more. So, secondly, don't smoke as many cigarettes. Try to cut down by one or two every day. OK? The next three points are to do with how you smoke. The most important is this: don't breathe the smoke in. It's when you breathe in the smoke that you do most damage to your health. Next, don't keep the cigarette in your mouth all the time. Pat it in an ashtray when you are not smoking it. And finally, don't smoke all the cigarette. The end of a cigarette is very dangerous to your health. So put the cigarette out after you have smoke half of it. All right? How many times has Christina tried to give up smoking?