题目内容：

    High school biology teacher Kelly Chavis knew smartphones were a problem in her class. But not even the students realized how much of a problem the devices were until Chavis did an in-class experiment.

For one class period, students used a whiteboard to count every Snapchat, Instagram, text, call that appeared on their phones. Chavis is among a growing number of teachers, parents and health experts who believe that smartphones are now partly to blame for increasing the levels of student anxiety. “One girl, just during the one hour, got close to 150 Snapchat notifications. 150!” she said.

Jean Twenge, a psychology professor at San Diego State University in California, said it is not a coincidence that youth mental health issues have risen with the number of phones. “This use of phones has led to a loss of sleep and face-to-face interactions necessary for their growth,” she said.

Researchers are still not sure whether phones cause student depression or depression causes phone use. But nearly 60 percent of parents said they worry about the influence of social media on their child’s physical and mental health.

Both schools and parents are starting to take steps to deal with the problem. Many public schools pay outside companies to watch students’ social media activity for signs of anxiety. Other schools invite in yoga teachers and comfort dogs to help calm students.

1.What’s the purpose of Chavis’s experiment?

A.To see how many students have smartphones.

B.To find out how popular her students are.

C.To show smartphones influence teenagers greatly.

D.To tell her students how to use smartphones wisely.

2.How did Kelly Chavis feel about the result?

A.Shocked. B.Excited. C.Satisfied. D.Frightened.

3.Which of the following is true according to Jean Twenge?

A.Students are now under great stress.

B.Students spend too much money on smartphones.

C.Over-using phones cause drops in students’ grades.

D.Over-using phones may harm students’ body and mind.

4.What might be talked about if the passage is continued?

A.How other schools deal with students’ phones.

B.Whether the ways to handle phones are effective.

C.How some parents deal with their children’s phones.

D.Whether students are willing to give up using phones.