Thanks for the question! For why (C) is correct, take a look at the second paragraph starting on line 19. We’re told that more intensive forms of fish farming contribute to water pollution because of the generation of large amounts of waste which make it more likely for pathogens to spread. In other words, a causal link is being set up between intensive fish farming and the pollution. If you get rid of the cause, the effect should go away as well, and so it’s without these intensive production methods, we would expect to see a lower likelihood for such pollution. (B), on the other hand, is incorrect because we aren’t told about other types of pollution in the passage. We can’t make a comparison to those types of pollution, and so (B) is too strong of an answer choice. Make sure to be on the lookout when you see words such as “any,†as these choices tend to exaggerate the answer choice and make it too strong (though they’re not always wrong).
Hope this helps! Feel free to ask any other questions that you might have.