GRE reading comprehension?

Question

The following passage is given:>Recently an unusually high number of dolphinshave been found dead of infectious diseases, andmost of these had abnormally high tissueconcentrations of certain compounds that, even inlow concentrations, reduce dolphins’ resistance toinfection. The only source of these compounds in thedolphins’ environment is boat paint. Therefore, sincedolphins rid their bodies of the compounds rapidlyonce exposure ceases, their mortality rate shoulddecline rapidly if such boat paints are banned.Then there is the question:>Which of the following, if true, most strengthensthe argument?>>A- The levels of the compounds typically used inboat paints today are lower than they were inboat paints manufactured a decade ago.>>B- In high concentrations, the compounds aretoxic to many types of marine animals.>>C- The compounds break down into harmlesssubstances after a few months of exposure towater or air.>>D- High tissue levels of the compounds haverecently been found in some marine animals,but there is no record of any of those animalsdying in unusually large numbers recently.>>E- The compounds do not leach out of the boatpaint if the paint is applied exactly inaccordance with the manufacturer’s directions.The "answer" is **C**, but I don't understand why that is? Doesn't **C** have the opposite effect? Since boats don't directly come in contact with sea water after being painted, and the fact that they are exposed to the air for some time before use reduces the chances of these compounds to contaminate the sea. The only choice that seems to me to be relatively correct is **B**.

Answer 1

The answer is C because the passage is arguing that once boat paints are removed, the substances will stop harming marine life. The passage states, " since dolphins rid their bodies of the compounds rapidly once exposure ceases, their mortality rate should decline rapidly if such boat paints are banned". Answer C highlights the fact that IF all boat paints were removed, within a relatively short period of time, all damage to the marine life would be rectified. It therefore strengthens the primary point of the argument, which is that removal of boat paints would be beneficial to the marine life.

Answer B causes reasonable confusion, but when answering these types of questions, you want to be careful to pick a statement that strengthens the argument rather than restating a fact. The passage already states that the boat paints lower the dolphins' ability to fight infection, and answer B really just restates that claim.

I hope this is helpful!