Sea Otter declining 是一个global issue. 当然读托福和雅思，要有个很重要的理念，生态，环境，疾病...都可以是global issue的。我们在阅读和写作中，要体现出浸透了这个理念，分数容易高起来，毕竟思维上的接近才是根本性的。
新的要求：
托福综合写作是要求概述篇章要义的，对reading部分的精读和速读要求后，便要求概述了。尤其是阅读段，做题的时候，阅读段会在屏幕上出现，所以不允许摘写，要自己概括。练习的时候在读懂速度的基础上，开始做概括。
原文 概括
The sea otter is a small mammal that lives in waters along the western coast of North America from California to Alaska. When some sea otter populations off the Alaskan coast started rapidly declining a few years ago, it caused much concern because sea otters play an important ecological role in the coastal ecosystem. Experts started investigating the cause of the decline and quickly realized that there were two possible explanations: environmental pollution or attacks by predators. Initially, the pollution hypothesis seemed the more likely of the two.
常规的开头，sea otter减少有两种假设，环境污染和被捕杀，作者认同前者。
The first reason why pollution seemed the more likely cause was that there were known sources of it along the Alaskan coast, such as oil rigs and other sources of industrial chemical pollution. Water samples from the area revealed increased levels of chemicals that could decrease the otters' resistance to life-threatening infections and thus could indirectly cause their deaths.
首先是Alaskan海岸有已知的各种污染源，比如石油和其他化工原料。
Second, other sea mammals such as seals and sea lions along the Alaskan coast were also declining, indicating that whatever had endangered the otters was affecting other sea mammals as well. This fact again pointed to environmental pollution, since it usually affects the entire ecosystem rather than a single species. Only widely occurring predators, such as the orca (a large predatory whale), could have the same effect, but orcas prefer to hunt much larger prey, such as other whales.

同区域的其他哺乳动物比如海狮等也在减少，说明污染导致整个生态系统变差
Third, scientists believed that the pollution hypothesis could also explain the uneven pattern of otter decline: at some Alaskan locations the otter populations declined greatly, while at others they remained stable. Some experts explained these observations by suggesting that ocean currents or other environmental factors may have created uneven concentrations of pollutants along the coast.
第三，科学家们认为，sea otter下降有地区不均衡是因为洋流让污染浓度不均衡。