Question 21 is based on the passage you have just heard.

    ​​​​​​​ Almost everyone suffers from a headache occasionally. But some people suffer from repeated, frequent headaches. (19) A headache is important because it can be the first warning of a serious condition that could probably be controlled if discovered early. If a person removes the warning, day after day, with a pain-killer, he or she may pass the point of easy control. The professional name for covering up a symptom is “masking.” (20) A headache specialist once said, “Masking symptoms is not the best way of treatment. Sometimes it is wiser to stand still than to advance in darkness.” A headache often interferes needlessly with normal, happy living. The employee with a headache does less work. In a flash of temper he or she may upset fellow workers or customers, causing a direct or indirect loss to the organization. The mother with a headache suffers and disturbs the family. She upsets her husband and children. Rest, quiet and fresh air stop many common headaches. (21) Lying down and possibly falling asleep may help. One can often handle tension headaches by rubbing and pressing back neck muscles. Heat from an electric pad or a warm bath can also help. Because hunger may be overlooked as a headache source, one must make a habit of regular meals. If a meal must be postponed for more than an hour, a snack helps to avoid a hunger headache.

(21). What does the speaker say helps relieve the symptoms of common headaches?

解析：细节理解题。问题为：说话者认为什么能够减轻一般头痛的症状？原文中Lying down and possibly falling asleep may help可知，躺下或睡一觉会有帮助减轻头痛症状。与A Lying down and having some sleep（躺下睡觉）一致。