Source: Revised GRE PDF 2nd Ed. Section 3; #25 (p. 61)


Which of the following, if true, most strengthens

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? The levels of the compounds typically used in boat paints today are lower than they were in boat paints manufactured a decade ago., In high concentrations, the compounds are toxic to many types of marine animals., The compounds break down into harmless substances after a few months of exposure to water or air., 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., The compounds do not leach out of the boat paint if the paint is applied exactly in accordance with the manufacturer’s directions.

3 Explanations


Kalina Gajda

Can you explain why the answer is not B?

Apr 5, 2019 • Comment

Adam Lyons, Magoosh Tutor

Hey Kalina,
The argument is that banning this boat paint will reduce the mortality rate of dolphins. The toxicity of the paint to other marine mammals has nothing to do with dolphins. We are not concerned with how the paint affects other animals, just dolphins. That's why B is not relevant to the argument.

Apr 5, 2019 • Reply


Saddam Hossain

I do not understand if the passage says dolphins rid their bodies of the compounds rapidly (very quickly) then how can compounds that break down into harmless substances after months of exposure to water can be answer. Compound is taking much longer time while dolphins need to get rid of very quickly.

Apr 21, 2017 • Comment


Hi Fuad,

So, the conclusion of the argument is: if we stop putting boat paint in the water, dolphins will stop dying.

Now, this makes sense ONLY if the all the boat paint that is already in the water will eventually disappear. Otherwise, there will always be boat paint left over in the water.

(C) shows that the boat paint that is already in the water will break down, which supports the idea that eventually there will be no boat paint in the water and the dolphins will stop dying.

Apr 21, 2017 • Reply

S T Haque Boney

hi adam but the answer also states that those substances will break into harmful substances.

Jul 1, 2018 • Reply

Sam Kinsman, Magoosh Tutor

Hi there,

Make sure you read the answer choices carefully! It says that the compounds break down into "harmless substances," not harmful substances!

Jul 5, 2018 • Reply


Gravatar Chris Lele, Magoosh Tutor

Sep 21, 2012 • Comment

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