单选题 6. Recently an unusually high number of dolphins have been found dead of infectious diseases, and most of these had abnormally high tissue concentrations of certain compounds that, even in low concentrations, reduce dolphins' resistance to infection. The only source of these compounds in the dolphins' environment is boat paint. Therefore, since dolphins rid their bodies of the compounds rapidly once exposure ceases, their mortality rate should decline rapidly if such boat paints are banned.
Which of the following, if true, most strengthens the argument? ______

A、 The levels of the compounds typically used in boat paints today are lower than they were in boat paints manufactured a decade ago.
B、 In high concentrations, the compounds are toxic to many types of marine animals.
C、 The compounds break down into harmless substances after a few months of exposure to water or air.
D、 High tissue levels of the compounds have recently been found in some marine animals, but there is no record of any of those animals dying in unusually large numbers recently.
E、 The compounds do not leach out of the boat paint if the paint is applied exactly in accordance with the manufacturer's directions.

【正确答案】 C

【答案解析】 C：原文禁止使用船漆，这解决了化合物的来源问题。但如果化合物一直残留在海水中，那么海豚死亡率依然不会降低。所以借助这个选项提供的信息，化合物自己还会降解，这解决了水中化合物的存量问题。禁止使用船漆，不会有新的化合物；化合物降解，旧的化合物也会减少，于是海豚死亡率确实会降低。该选项属于直接加强原文结论。注意，很多考生认为这个选项是“寻找他因”，其实不然。如果是寻找他因，那么原文的原因和选项提供的原因应该是竞争关系。但是本题中，原文的原因是“禁止使用船漆”，该选项的原因是“化合物降解”，选项对于原文起到促进作用，而非竞争关系。
A：根据该选项，只需要使用今天生产的船漆而非十年前的，依然可以减少海豚的死亡率。该选项起到削弱作用，不选。
B：原文中化合物对于海豚来说是有毒的，这是一个事实。因此，即使化合物对于很多动物来说是有毒的，依然无法加强这个事实。不选。
D：并不确定该选项里的“很多海洋动物”是否包含了原文的海豚，无关选项，不选。
E：该选项的错误原因同选项A，都起到削弱作用，不选。