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.