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71. Identifying the reasons for an emerging phenomenon which involves several complicated factors is far from an easy task . For example , some scientists attribute environmental deterioration to a series of natural factors , while others place the blame solely on inappropriate human behavior . 要找到涉及许多复杂因素的新现象的原因远非一件易事。例如，一些科学家把环境的恶化归结为一些自然因素，而另一些人把责任都推在人类不适当的行为上。 72. One doesnt have to look far to realize the direct correlation between smoking and cancer . 人们不用花费很大力气就能发现抽烟和癌症之间的直接联系。 73. The explanation for the phenomenon of the rising teenage suicide rate involves many complicated factors . Some attribute the rise to an overemphasis on early success , others point to mounting peer pressure , and still others to confusion over changing social values . 对上升的少年自杀率的解释涉及很多复杂的因素。有的人把上升的原因归结为过分强调少年时期的成功，有的人指出是因为不断增长的同伴之间的压力，还有人认为是对不断变化的社会价值的迷茫造成的。 74. The reasons for antisocial behavior are both complicated and varied . I suggest the phenomenon results from inappropriate role models and the lack of well-defined norms of behavior . However , the main reason is quite likely the continuing degeneration of social values . | 
