71.Our first reaction to the suggestions was one of utter astonishment. Nonetheless，simply discussing related issues suggests a starting point for finding solutions.

72.What does the future hold if mankind persists in wasting natural resources? While no one knows for sure，scientists do exhibit a degree of certainty when predicting that future generations will face a dramatically different world.

73.Reversing undesirable social trends will be far from an easy task and will require a dramatic change in attitudes. A keen awareness of right from wrong is essential for determining appropriate social behavior.

74.Achieving the impossible is quite obviously an oxymoron(figure of speech that uses seeming contradictions).Therefore，succeeding at a difficult task requires great effort.

75.We owe a debt of gratitude to the many individuals who dedicated their lives to making the world a better place. However，we must not rest on their accomplishments，but must instead work assiduously to record even greater achievements.

76.There are indeed many problems requiring urgent attention，but concerted efforts on our part will eventually lead to final solutions.

77.The two major challenges facing China today center on maintaining sustained economic growth and feeding its growing population of over1.2 billion people with only seven percent of the world s cultivable land. Despite the monumental difficulties involved，Chinese people will undoubtedly exhibit their indefatigable resilience and achieve great success in both regards.

78.We do，in fact，have a long way to go to reach our final goal

but achieving some remains well within the realm of possibility.

79.The time is right for us to take full advantage of ample existing opportunities.

80.While it remains to be seen whether or not environmental deterioration can be controlled，the current prospects are far from encouraging. People around the world must act immediately to prevent the situation from deteriorating even further.