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托福综合写作优秀作文，相信这个问题是许多正在准备留学的同学关心的一个问题，那么下面小编就来和大家说一说，感兴趣的您赶紧往下了解吧。

托福综合写作优秀作文

The lecturer and the reading passage suggest two competing theories, the predation theory vs. the pollution theory, to explain why the sea otter population is in rapid decline.

The professor reasons that the absence of dead sea otters washed up the coast suggests that their decline is not caused by sea pollution but rather by sea predators who consume their bodies after killing them. In contrast, the reading passage attributes the death of sea otters to pollution, citing evidence of increased sources of ocean contaminants which lead to greater vulnerability to infections.

Furthermore, the lecturer argues that orcas are likely factors in the disappearance of sea otters, because the scarcity of whales, their usual prey, has left them with no other choice but to start hunting smaller mammals like the seals for food. The reading passage, on the other hand, rules out this theory based on the orca’s praying habit, and instead approves of the pollution theory as the only explanation for the decline of both large and small sea mammals across the entire ecosystem.

Finally, according to the lecturer, the uneven pattern of sea otter decline corresponds to the distribution of the orcas; she argues that the fact that their population has declined most rapidly where orcas are most prevalent further validates the predation theory. However, the reading passage argues that changeable environmental factors, which lead to different concentrations of pollutants, better explains the varying pattern of sea otter decline.

满分托福综合作文

The reading states that fuel-cell engines have several advantages over internal-combustion engines. However, the lecturer points out that replacing internal-combustion engines with hydrogen-based fuel-cell engines is technologically unfeasible, environmentally unfriendly, and economically unviable.

First, the lecturer argues although, as the reading states, hydrogen resource are abundant in various resources, it cannot be utilized before being turning into liquid state, which is hard to produce and store technologically. For example, it must be kept cold at minus 253 degrees Celsius which can only be realized with elaborate cooling technology.

Second, the lecturer refutes the claim in the reading that hydrogen cells are environmentally friendly. She argues that although engines that use hydrogen cells produce less pollution, the manufacturing of hydrogen cells generates large amounts of harmful by-products due to the burning of fossil fuels in the purification process.

Third, although the reading suggests that hydrogen-based engines are more fuel-efficient and thus economically competitive than internal-combustion engines, the professor argues that such an advantage is undermined by the fact that fuel-cell engines are extremely expensive to manufacture because they require the addition of platinum, a very rare and expensive material.

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