1. C. New explanations for the obesity epidemic.

　　2. A. gained the least weight

　　3. B. it causes sleep loss

　　4. D. It contributes to our weight gain.

　　5. C. It suppresses their appetite.

　　6. D. Those who quit smoking.

　　7. B. the rising proportion of minorities in its population

　　8. unclear

　　9. family size

　　10. partly genetic

　　简短回答问题

　　47. lighter and more absorbent

　　48. the potential in the U.S.

　　49. established athletic footwear industry

　　50. informally

　　51. The team spirit and shared values of the athletes

　　仔细阅读

　　52. B. By its sustainability

　　53. D. the decrease of brodiversity

　　54. C. They are not necessarily sustainable.

　　55. A. It will go through radical changes.

　　56. D. To urge people to rethink what sustainable agriculture is.

　　57. A. They were of inferior races.

　　58. B. They can do just as well as their predecessors.

　　59. D. They may forever remain poor and underachieving.

　　60. C. Prevent them from being marginalized.

　　61. B. how to help immigrants to better fit into American society.