A、120. B、100. C、70. D、17. C细节题。对话开始时Frank说：I gave out 120 copies and I got 70 back，故C为正确答案。A，B，D均和原文相悖。

Theresa: Hi, Frank, your survey sounds very good. How many people filled it in?
Frank: I gave out 120 copies and I got 70 back.
Theresa: That’s a very high rate of return. Who did you give your questionnaires to?
Frank: I gave a copy to every student in my hall of residence and a few to friends from other colleges.
Theresa: Don’t you think that this will influence your results?
Frank: What do you mean, Theresa?
Theresa: The people in your hall of residence will all be about the same age. They are all students, most of them studying similar subjects and from similar backgrounds. Therefore it is likely that they will have similar opinions. Your results represent student opinion, not public opinion.
Frank: So how are you going to do your research?
Theresa: I’m going to interview my respondents in the shopping mall. I’ll ask them some multiple-choice questions and tick off their answers on my sheet. That way I can select people of all ages and attitudes, so my sample should be reasonably representative.
Frank: Isn’t it very difficult to ask meaningful questions using multiple choice?
Theresa: Yes, it is, but the secret to writing a successful survey is to write simple multiple-choice questions that target the information you are looking for. Therefore, it is better to write a lot of short specific questions than longer general ones.
Question 6
How many survey copies did the man get back?
(pause: 10 seconds)
Question 7
Why does the woman think that the man’s survey respondents will influence his results?
(pause: 10 seconds)
Question 8
What does the woman think about a good survey?
(pause: 10 seconds)
Question 9
Where is the woman going to conduct her survey?
(pause: 10 seconds)
Question 10
According to the woman, what is the secret to conducting a successful survey?