[解析]
(1)细节理解题。由第一段中的But research now suggests that the main reason for the students' rising anxiety levels is something else. (但现在的研究表明,学生焦虑水平上升的主要原因是其他原因)和第二段中的Last year,in the journal Pediatrics three researchers wrote that too much social media use might contribute to the development of mental health problems in teenagers,such as loneliness,depressive symptoms and anxiety. (去年,在《儿科》杂志上,三位研究人员写道,社交媒体使用过多可能会导致青少年心理健康问题的发展,如孤独、抑郁症状和焦虑)可知,青少年心理问题的主要原因是沉迷于社交媒体。故选D。
(2)推理判断题。由倒数第二段中的Emily Mogavero,a 17﹣year﹣old student in New York,said"I definitely feel stressed to keep up my information and stuff.It kind of worries me that I'm on my smart phone so long." (17岁的纽约学生Emily Mogavero说:"面对如此多的信息和资料,我确实感到压力很大。我有点担心我用智能手机太久了。)可推断出Mogavero认为过度使用智能手机令人担忧。故选A。
(3)细节理解题。由最后一段中的Some parents are not letting their children get smart phones until they grow up.A teacher,Erin Schifferli,says her 12 yearold daughter,Aeva,won't get a phone until she is 16 years old. (一些家长在孩子长大之前不让他们得到智能手机。一位名叫艾琳•希弗利的老师说,她12岁的女儿埃娃要到16岁才能拿到手机)可知,有些父母阻止他们的孩子使用智能手机。故选B。
(4)推理判断题。由第二段Jean Twenge说的话What a lot of teens told me is that using social media and their phones seems forced.This use of phones has led to a loss of sleep and face﹣to﹣face interactions. (很多青少年告诉我的是,使用社交媒体和手机似乎是被迫的。这种使用手机的方式导致睡眠不足和面对面交流的缺失)第二段中的Last year,in the journal Pediatrics three researchers wrote that too much social media use might contribute to the development of mental health problems in teenagers,such as loneliness,depressive symptoms and anxiety. (去年,在《儿科》杂志上,三位研究人员写道,社交媒体使用过多可能会导致青少年心理健康问题的发展,如孤独、抑郁症状和焦虑)可知,过度使用手机会影响青少年的社交互动。故选C。