015. The Audubon Society and other conservation groups, concerned over what they perceive as the serious threat to the environment posed by the policies of the government, are preparing for a major political effort.
=The Audubon Society and other conservation groups/, concerned over/ what they perceive as the serious threat to the environment/ posed by the policies of the government/, are preparing for a major political effort.
# Audubon 社团和其他谈话组织/，。
*这句话虽然不长，却较难理解，原因是句子的主要内容，也就是 concern over 后的内容比较复杂。但是我们不需要去搞清楚语法上这个句子是怎么形成的，我们只需把内容理解即可，所以不要花时间考虑语法，记住不看语法看内容。Audubon 属于认识就反映不认识就过去的词类，但从后面的 other conservation groups 我们可以知道 Audubon 社团是一个谈话组织。
016. The animosity between those who regulate and those who are regulated has never been more pronounced than in recent debates over environmentalism and pollution control.
=The animosity/ between those who regulate and those who are regulated/ has never been more pronounced/ than in recent debates/ over environmentalism and pollution control.
#敌意/在管理者和被管理者之间/激烈地表现出来/在 近的辩论中/关于环境保护主义和控制污染。
*这句话可以称之为短小精悍，句子不长，圈子却没少绕。who regulate 和 who are regulated，应该是两种人，也就是管理者和被管理者。has never been more…，从没有更…,也就是 …，这样的反向理解可以更好的理解句子的意思，比如双否就可以理解成肯定。
017. Some psychiatric studies indicate that among distinguished artists manic depression and major depression are ten to thirteen times more prevalent than in the population at large.
=Some psychiatric studies/ indicate/ that among distinguished artists/ manic depression and major depression/ are ten to thirteen times more prevalent/ than in the
population at large.
#一些心理研究/表明/在杰出的艺术家中/躁狂抑郁症以及主要的抑郁症/高出 10 至 13 倍/比整个人口(的平均水平)。
* manic depression 属于认识就反映不认识就过去的词类。根据句意 at large 本来可以不琢磨，但是笔者将其加上黑体字，就是想告诉读者，英语中有很多俚语，俗语是不能靠猜测而知道其意的，这类词语要靠平时积累，不过好在 GRE GMAT 中这种短语并不是很多。