【正确答案】 D、E

【答案解析】woman： Hi, Mathew. I heard that you are doing a research on childhood obesity, aren't you? man： Yes, indeed. I've been trapped in this matter for a long time. woman： Glad that you are doing something meaningful. Anyway, how is it going? man： I'd like to say, not very well. I am thinking maybe I have done it wrong. Maybe I can never get a conclusion, it is a total failure. woman： What’s the matter? man： You know, I distributed some questionnaires in a primary school nearby. Then the problems began. woman： Yeah? If the questionnaires are not proper, why not get them back? man： Not quite true. I asked the teachers to supervise the students to ensure that each and every questionnaire would be filled out. But what really worries me is that I have got lots of similar or even exactly the same answers. woman： Oh, the children must copy their friends or classmates. man： That is right. It is unavoidable to be influenced by their friends. Besides, I found the data we’ve got is not that accurate anyway. woman： Oh, how is that possible? man： Well, as children grow older, the influence of certain factors on obesity will decrease, so the answers we've got from the questionnaires might be out of date soon. Things are always changing.