听力原文：W: Welcome to our programme, Mr Smith. M: Thank you. W: Mr Smith, how long have you been a police officer? M: Ive been a police officer for thirty years. W: Thirty years. And youve had different types of assignments on the police force, I guess. M: Yeah, Ive done everything from patrol to undercover work to detective work, and now Im supervising investigations. W: Mr Smith, I think most people would say that being a police officer is a very stressful job. Would you agree? M: Yes, its definitely a stressful job. But it depends on your assignment. W: So, whats probably the most stressful job you can have? M: Id say patrol is the most stressful assignment. W: Thats interesting! In what way? M: Well, I guess the biggest part of the stress is the fear factor, the fear of the unknown. W: What do you mean, Mr Smith? M: Well, in patrol work, you dont know from moment to moment who you are talking to or what their reaction is going to be to justify your presence. Lets say, for example, a patrol officer stops someone for a traffic violation. It seems as though that would be a very low-stress situation. W: Yes, it is a very low-stress situation. M: But the truth is, there are more police officers injured during a routine stop. W: Really? M: Really! Thats why all police officers are taught from the very beginning to be aware of their surroundings: people back over policemen, people shoot policemen, people jump out at policemen — different kinds of things. So thats probably the most stressful time. W: I see. Lets take a break and then well move on to our next topic. M: All right. Questions 9 to 12 are based on the conversation you have just heard. 9. Whats the relationship between the two speakers? 10. What do we know about Mr Smith from the conversation? 11. What assignment does Mr Smith believe is the most stressful? 12. Why are all police officers taught to be aware of their surroundings from the very beginning?10．