阅读理解：

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.