A、Do not buy their children smartphones. B、Put off buying their children smartphones. C、Buy their children smartphones as early

W: Now how our increasingly wireless world is affecting our social behavior, especially among the generation that has grown up with smartphones? William Brangham will tell us about it.
M: The promise of social media is that it connects us to each other, and helps us become more social. But according to my study, for many teenagers, greater use of social media means a far greater sense of isolation.
W: True. Teenagers now spend less time in the company of their friends. They date less, and get less sleep than earlier generations. And with this growing isolation comes a rise in cyber-bullying, feelings of being left out, and higher rates of depression and suicide.
M: So, smartphones and social media have had this very detrimental effect on a younger generation.
W: You write in the study that rates of teen depression and suicide have skyrocketed since 2011. What is the evidence that these things are caused by heavy use of these devices?
M: Well, the research that I did was correlational. So, proving causation, really, you need a different type of method. But, fortunately, there are two studies that have looked at adults over time and seeing that, when they use social media more, their psychological well-being goes down and mental health problems increase.
W: And you feel confident that this effect could not be caused by other factors in society, the economy, employment, access to health care, so many other things that could drive our sense of well-being?
M: Yes, so I looked at the economy, and of course, the great recession had a big effect on people. Unemployment really went up. But if you look at the pattern for unemployment, for example, a good indicator of the strength of the economy, unemployment really peaked out at about 2010, and then went down, and is now quite low. But the data for mental health goes in the other direction. It doesn’t do a whole lot until about 2011 or 2012. So, unemployment doesn’t seem to be the answer.
W: Last question. What kind of advice would you give parents?
M: Well, I think, put off getting teen a smartphone as long as you can.
Questions 1 to 4 are based on the conversation you have just heard.
1. What does the man find out about the link between social media and teenagers?
2. What is the effect of social media on teenagers according to the woman?
3. How does the man define the effect of social media on the youth?
4. What is the man’s advice to parents?