A、Sleeping problems. B、Stomach problems. C、Bad emotions. D、High blood pressure. B短文提到，长期过量喝咖啡会导致胃部和牙齿出现问题。B对应其中一个负面影响，故正确。

Coffee can be considered one of nature’s greatest gifts. It gives mental and emotional clarity without harmful side effects, and it contains a wealth of nutrients. Yet, when most people drink coffee, they are not thinking that the beverage is improving their health. In fact, some may even feel a little guilty, since some believe coffee isn’t good for you at all.
    The truth of the matter is: coffee, like anything else, can cause problems if too much is consumed. In the short-term, too much coffee will cause sleeping problems and hypertension. In the long-term, too much coffee will cause stomach problems as well as teeth staining.
    As far as the benefits, moderate consumption of coffee, which means 1 to 4 cups a day, provides your body with a wealth of antioxidants. These substances are responsible for eliminating free radicals. They are the chemical byproducts produced any time your body does something. A small number of them can help serve as a buffer against negative elements, but if they aren’t kept in check, they can cause health problems. Antioxidants ensure that this doesn’t happen.
    Even the caffeine content within coffee can be beneficial toward your health. One way it does this is by cleaning the water of your body’s cells, which keeps your weight down while cleaning out impurities.
20 Why do some people feel guilty when they drink coffee?
21 What will drinking too much coffee cause in the long-term?
22 In what way can caffeine benefit one’s health according to the speaker?