Question ID:PT16 S2 Q4 Passage:Although water in deep aquifers does not contain disease-causing bacteria, when public water supplies are drawn from deep aquifers, chlorine is often added to the water as a disinfectant because contamination can occur as a result of flaws in pipes or storage tanks. Of 50 municipalities that all pumped water from the same deep aquifer, 30 chlorinated their water and 20 did not. The water in all of the municipalities met the regional government’s standards for cleanliness, yet the water supplied by the 20 municipalities that did not chlorinate had less bacterial contamination than the water supplied by the municipalities that added chlorine. Stem:Which one of the following, if true, most helps explain the difference in bacterial contamination in the two groups of municipalities? Correct Answer Choice:EChoice A:Chlorine is considered by some experts to be dangerous to human health, even in the small concentrations used in municipal water supplies. Choice B:When municipalities decide not to chlorinate their water supplies, it is usually because their citizens have voiced objections to the taste and smell of chlorine. Choice C:The municipalities that did not add chlorine to their water supplies also did not add any of the other available water disinfectants, which are more expensive than chlorine. Choice D:Other agents commonly added to public water supplies, such as fluoride and sodium hydroxide, were not used by any of the 50 municipalities. Choice E:Municipalities that do not chlorinate their water supplies are subject to stricter regulation by the regional government in regard to pipes and water tanks than are municipalities that use chlorine.