A、They are not harmful to the brain. B、They have more benefits than harm. C、They are not worth the price at all. D、They are valu

Many people suffer from some form of extreme anxiety. Some experience occasional attacks of panic for almost no reason. Others go around in a state of continual uneasiness. How do we control anxiety? [16]The best way is to take drugs that help patients manage their anxiety. Patients who take these drugs say that they are able to work, to sleep and to go to places they feared to visit before.
    But the effects of the drugs on the human body, especially on the nervous system have not been known for a long time.
    Scientists have started a series of studies to identify the effects of the drugs on the brain and have gained some insight into the costs and benefits of the anti-anxiety drugs. They are valuable because they can reduce the effects of expected failure, frustration and disappointment. [17]But their value demands a price. Two effects of the drugs are obviously harmful. [18]First, they weaken a person’s ability to react to changes; second, they fail to help a person deal with unexpected troubles. It is fairly sure that people will meet with problems they have never expected, so [17]these harmful effects may make the price of anti-anxiety drugs too high.
16. According to the speaker, what is the best way to manage anxiety?
17. What does the speaker say about the anti-anxiety drugs?
18. What harmful effect do the anti-anxiety drugs have?