A、They do much more exercise than others. B、They cat less than those who gained much weight. C、They perform those small motions.

M: You don’t know about me is that I used to weigh an incredible three hundred pounds. Ever since I started the weight loss program, though, I’ve been slimming and trimming until I’m now in the spectacular shape you see today.
W: Don... you look the same as you always have.
M: Well, okay. But I do fidget.
W: You fidget? What does fidgeting have to do with weight?
M: Maybe a lot! Researchers at the Mayo Clinic in Minnesota did some experiments to try to figure out why some people gain weight more than others do.
W: Boy, I can relate to that. Some people can eat whatever they want and they never seem to gain a pound.
M: In this study, volunteers were given a thousand extra calories a day— about two cheeseburger’s worth of extra intake.
W: This kind of study I’d like to be in!
M:(10)Well anyway, they also wore special devices that recorded how much they moved—you know, walking up and down steps and whatnot. Everybody gained weight, but some people gained much less than others. The reason? Fidgeting.
W:(11)You mean just drumming your fingers or scratching your neck or something?
M:(9)/(11)Any motion takes energy to perform. And little motions like rearranging things on your desk or stretching your back, if you do them all the time, start to add up. We generally only think of large motions, like exercise, as burning calorics. But people who have the fidgets may be doing a slow, steady burn all day long.
Questions 9 to 12 are based on the conversation you have just heard.
9. According to the dialogue, how to lose weight efficiently?
10. How can researcher perform the study?
11. Which of the following action has nothing to do with losing weight?
12. Why some people gained much less than others?