托福综合写作课件.ppt

例子和解释是重点 尽可能详细 以词为单位 Listening L R M: hyd FC promis/ alter advan hyd available/renew Ex: plenti—gas/ solve pollu Ex: water—produ no CO2 economi/ Ex: effici/ less energy M: hyd not solut to pollut not easily avail Ex: liquor state—difficult store—cooling not practi not solve probl-cars produ hyd—pollut Ex: coal/oil burn –pollut – factory—pollut expensi Ex: made of p—expen effort—repla—not success 综合写作听力 用缩写表示名词概念、动词、部分形容词 用符号替代逻辑关系 结构：1、2、3 因果：→ 转折 增加或减少 大于或小于 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. 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. 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. Third, scientists believed that t