參考答案：

　　56. C) The decline of the grain yield growth.

　　57. A) Their self-sufficiency is vital to the stability of world food markets.

　　58. D) They focus more on the increase of animal feed than human food grains.

　　59. D) The world will be able to feed its population without increasing farmland.

　　60. B) It is based on a doubtful assumption.

　　61. A)More men taking an extended parental leave.

　　62. C) Their number is too small to make a difference。

　　63. A) A long leave will have a negative impact on their career.

　　64. C) Surprise

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