solve the problem in a tender（和善的）way.

21. The purpose of the first paragraph is to_________.

　A. show a disagreement of views

　B. serve as a description of teenager trouble

　C. show the popularity of teenager problem

　D. serve as an introduction to the discussion

22. Which of the following is NOT the advice given in the passage?

　A. Try to think of ways to balance family event with friend event.

　B. Don't feel angry if your parents ask you to do something.

　C. Tell your parents before you decide to spend time with your friends.

　D. Advise your parents to do something that you are interested in with you.

23. What's the purpose of the passage?

　A. To inform us of parent and teenager tension.

　B. To tell us about a common teenager problem.

　C. To advise teenagers how to deal with their tension with their family.

　D. To persuade parents to show consideration for teenagers.

　　The world's first robot police officer has started working. Its name is 'RoboCop' and it went into service for the Dubai Police earlier this week. Robocop's first official duty was to greet guests at the opening of a security(安全) conference in Dubai. Apart from greeting visitors, its job was to answer questions and give directions. RoboCop has a built-in tablet for people to interact(互动) with. People can use the tablet to pay traffic fines and use other smart police services. The tablet is linked to a police station, so people can talk to human police officers. In addition, RoboCop can speak six languages, including English and Arabic. The 170 - centimetre - tall robot can also shake hands, salute(致敬) people and recognize people's emotions and facial expressions.

　　Dubai Police says RoboCop is the first of many robot police officers for the city. A spokesman said that by 2030, 25 per cent of the Dubai Police force will be robots. He said: "We are looking to make everything smart in Dubai Police. By 2030, we will have the first smart police station that won't require human employees."

"The RoboCop is the latest smart addition to the police force and has been designed to help us fight crime, keep the city safe and improve happiness levels," He added. He also said that RoboCop would, "assist and help people in the malls(购物中心) or on the