In the first sentence, does "abatement" mean "reduce" or "total elimination," like reducing to 0?

The critic uses the whole example with the rivers to conclude that using electric cars wouldn't necessarily result in total elimination of pollutants, but what if the rivers were dammed? Wouldn't that mean the proponents of the electric car can still be correct? Or would that be going beyond the stimulus?

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https://classic.7sage.com/lsat_explanations/lsat-june-2007-section-2-question-08/