题目内容：

    How much time do you spend in front of a screen every day？ If your answer is about one hour，then maybe you are one of the ____ teenagers in the world．

Scientists did a ____． They asked students aged 13 to 18 how long it ____ them to have fun on phones and computers． They also asked about ____ feelings of happiness． They found that those who spend more time on their smart phones are unhappier． "Spend no more than two hours a day on digital media（电子产品），___ try to spend more time with friends and on exercise． These two activities bring greater happiness．" Jean Twenge， the scientist who led the study ，said．

1.A. happy B. happier C. happiest

2.A. survey B. discovery C. test

3.A. takes B. spends C. costs

4.A. your B. our C. their

5.A. but B. and C. or