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 force more on the increase of animal feed than 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. B) People's changing attitudes towards family.

　　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. B) Surprise.

　　65. D) They will still face the difficult choice between career an children.