A、Eating disorder. B、High blood pressure. C、Tiredness. D、Weight problem. C短文开头提到，患有失眠症的人很难人睡，睡眠质量不好，白天往往会感到疲惫、心烦意乱、注意力无法集中。

Insomnia(失眠症)is the most common sleeping disorder. Approximately 25% of the adult suffer from sleeping problems, and as many as 10% reach the threshold of insomnia.(23)Insomniacs experience difficulty falling or staying asleep, a lack of healthy sleep, and daytime symptoms such as fatigue, mood disturbance, and difficulty concentrating. For insomniacs, theirs is often a long-term condition. Nearly 70% continue to experience symptoms a year later, and half still have insomnia up to three years later. Compared to the general population, people with insomnia are more than five times as likely to experience anxiety and depression, are at more than twice the risk of developing heart disease, and may have a high risk of death. Insomniacs may also be at significantly greater risk of alcohol and substance abuse.(24)But despite the large number of people affected, insomnia often goes unrecognized and untreated. People usually ignore their sleeping quality and mental condition. According to the experts, much more needs to be done to identify and treat insomnia in its early period. Furthermore, efforts must be made to ensure that patients are treated according to clinical guidelines and with treatments of proven effectiveness. Some of the most commonly prescribed drugs have been poorly studied for treatment of insomnia.(25)The problem is more pronounced for non-prescription drugs. Despite the widespread use of over-the-counter products, such remedies have not been rigorously studied and there is little evidence to indicate which drugs, if any, work well and for whom.
23. What kind of difficulty do insomniacs suffer?
24. What can we infer from the passage?
25. What can we learn about over-the-counter products?