本题是继《阅读长难句分析基本原理》后的练习篇，把所掌握的技巧，应用的实际练习当中，进一步夯实自己的阅读能力。
练习步骤：
step1：划分句子结构，找句子主干
step2: 确定修饰词，修饰短语或修饰从句的修饰关系
step3: 确定代词指代对象
剑桥雅思9
Reading Passage 2
长难句：For example, we have had civilization on Earth for perhaps only a few thousand years, and the threats of nuclear war and pollution over the last few decades have told us that our survival may be tenuous.