A、Lack of physical activities among all Americans. B、The abundant provision of rich foods. C、The belief that weight cannot be co

Public interest was aroused by the latest discovery of a changed gene in obese mice. The news was made known by Rockefeller University geneticist Jeffrey Friedman. The researchers believe this gene influences development of a hormone that tells the organism how fat or full it is. Those with the changed gene may not sense when they have eaten enough or if they have sufficient fatty tissue, and thus can’t tell when to stop eating. The researchers also reported finding a gene nearly identical to the mouse obesity gene in humans. The operation of this gene in humans has not yet been demonstrated, however. Still, professionals like University of Vermont psychologist Esther Rothblum reacted enthusiastically. This research indicates that people really are born with a tendency to have a certain weight, just as they are to have a particular skin color or height. Actually, behavioral geneticists believe that less than half of the total weight variation is programmed in the genes, while height is almost entirely genetically determined.
   Whatever role genes play, Americans are getting fatter. A survey by the Center for Disease Control found that obesity has increased greatly over the last 10 years. Such rapid change underlines the role of environmental factors, like the abundance of rich foods in Americans’ overeating. The Center for Disease Control has also found that teens are far less physically active than they were even a decade ago. Accepting that weight is predetermined can relieve guilt for overweight people. But people’s belief that they cannot control their weight can itself contribute to obesity.
   Questions 12 to 15 are based on the passage you have just heard.
   12. What does the speaker say has aroused public interest?
   13.What do we learn about the changed gene?
   14.What does University of Vermont psychologist Esther Rothblum say?
   15.What accounts for Americans’ obesity according to a survey by the Center for Disease Control?