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

听力原文

        People spend a lot of time using phones and computers. Much of that time is devoted to text messages and social media. But many people choose to spend their time playing computer games. For years, parents and teachers have worried that these games might be addictive. (19) [And now the World Health Organization has recognized addiction to computer games as a disease.] The organization explains that this decision reflects general agreement among experts around the world that some people have a problem with these games. They show a pattern of behavior characterized by a lack of control. (20) [Such people make computer games a priority over their responsibilities. They may play games instead of attending school or work or socializing.] According to the World Health Organization experts, people’s use of computer games is different from their use of the Internet, social media and online shopping. These experts claim there is not sufficient data to indicate that people’s reliance on those other activities is an addiction. But they argue that playing computer games to excess is different. This behavior can become a disorder. To meet the new definition for addiction, the behavior must damage a person’s relationships or performance at school or work. And this must last for at least a year. Still, not all behavior experts agree. (21) [Some argue that there is not enough research on the subject. Thus, they claim it is too early to call computer game addiction a disorder.]

21. What do some behavior experts think of addiction to computer games?   （一些行为专家对电脑游戏成瘾有什么看法？）解析：D。录音结尾提到，有些行为专家认为，对这一问题的研究还不够（not enough research on the subject）。因此，他们声称现在把电脑游戏成瘾称为一种疾病还为时过早。D项中的not enough为原词复现，evidence对应录音中的research，故D项正确。

错项排除：A项和C项在录音中未提及，故排除。录音中只是说关于将电脑成瘾归为一种疾病的说法，有些专家提出不同意见，但并没有说永远无法达成共识，故B项错误。