题目内容：

Recently, a series of bracelets have gone viral on Weibo. On these specially made bracelets are the words “Cell Phone Ninja.”

The bracelets are actually part of an experiment carried out by Chongqing Three Gorges University that challenges students not to use cell phones in class for 21 days.

The experiment started on April 12. Each student who volunteered to participate received a bracelet. Before the first class and after the last class of each day, students were instructed to upload a photo of their bracelet to the school’s public Wechat account if they did not use their cell phones.

Over 800 students signed up for the experiment and 400 were selected to participate. After seven days, only 103 students remained. The experiment was set for 21 days because of a claim in psychology that 21 days is the length of time required to form any habit.

According to the teachers monitoring the activity, there were no rewards or punishments in the experiment. It depended on students themselves to make the decision. Teachers hope students can form better study habits through activities like this one.

1.What should the student do in the experiment?

A. The student should receive a bracelet.

B. The student should upload the bracelet’s picture during their class.

C. The student should upload the bracelet’s picture before and after their class.

D. The student should open an account in the school’s public Wechat.

2.How many students survived the experiment after a week?

A. 800.         B. 400.         C. 203.         D. 103.

3.Why did the experiment last for 21 days?

A. Because the 21st day is a special day in psychology.

B. Because the organizers only have 21 days free.

C. Because it is believed that it takes 21 days to develop a habit.

D. Because 21 days are needed to form any hobby.

4.According to the teachers monitoring the activity, through such activities ________.

A. students must form a better study habit

B. students could benefit from the activity

C. students should depend on themselves to make a choice

D. few students attended it because there were no rewards or punishments