56. D) They are major contributors to environmental problems.
57. C) The desire to generate profits.
58. C) They believe building such a system is too costly.
59. A) It helps businesses to save and gain at the same time.
60. B) They do much better than their counterparts in terms of revenues.

精品四六级考试课程:英语四级【签约班】  英语六级【签约班】  英语零基础直达CET4级考试版