听力原文：W: Alex is an English teacher in Iran and today wed like to share his experience as a teacher. So welcome Alex. How do you enjoy teaching English as a foreign language? M: I like teaching students how to speak. And I really enjoy seeing them learn and improve. Ive been teaching for five years now, and Ive got good experience from my classes. I teach in institutes and also universities and theyre a bit different. People who come to institutes are highly motivated because they come with their own legs. As they say, and as we say, theyre quite interested. They try to be active. But for the students at universities, because they have to pass some courses, they might not be interested enough most of the time. W: Well, you say that recently youve been trying to be a creative teacher, and to stimulate students. So tell me about that. M: Well, most of the time I try to make them motivated by just making the class more fun and interesting. W: What do you find is the hardest part of being a teacher? M: Well, the hardest part is that a teacher has to forget everything in his life before going to a class. W: What do you mean by that? M: You see, if you are sad, if you have a lot of ups and downs in your life, when you enter a class, you have to be a teacher full of energy, very happy. You have to forget about all your problems. If you just take your problems to the class, you wont be a good teacher. Questions 13 to 15 are based on the conversation you have just heard. 13. Why does Alex enjoy his teaching job? 14. What is the characteristic of institute students? 15. What is the hardest part of being a teacher according to Alex?14．