Columnist: The amount of acidic pollutants released into the air has decreased throughout the world over the last several decades. We can expect, then, an overall decrease in the negative environmental effects of acid rain, which is caused by these acidic pollutants. Each of the following, if true, would weaken the columnist's argument EXCEPT: ['Some ecosystems have developed sophisticated mechanisms that reduce the negative effects of increased levels of acids in the environment.', 'The current decrease in acidic pollutants is expected to end soon, as more countries turn to coal for the generation of electricity.', "The soils of many ecosystems exposed to acid rain have been exhausted of minerals that help protect them from acid rain's harmful effects.", 'The effects of acid rain are cumulative and largely independent of current acid rain levels.']