Although water in deep aquifers

Answer choices

1. A

   No Impact4% picked this

   Chlorine is considered by some experts to be dangerous to human health, even in the small concentrations used

   Whether chlorine itself is dangerous to health is a separate question from whether chlorinated water has bacterial contamination. The paradox is about bacteria levels in the two groups; chlorine's safety profile does not bear on why the non-chlorinated water has fewer bacteria.

   4%
2. B

   No Impact1% picked this

   When municipalities decide not to chlorinate their water supplies, it is usually because their citizens have voiced objections to the

   Citizen objections to chlorine's taste explain why some municipalities chose not to chlorinate, but they do not explain why those municipalities have less bacterial contamination. Reasons for not chlorinating do not bear on what makes the water cleaner.

   1%
3. C

   Cheats Paradox5% picked this

   The municipalities that did not add chlorine to their water supplies also did not add any of the other available water disinfectants,

   If non-chlorinating municipalities also did not use any other disinfectant, then they had less protection against bacteria than the chlorinators — yet still ended up with less contamination. This deepens the puzzle rather than resolving it. The non-chlorinators should have more bacteria, not less.

   5%
4. D

   No Impact2% picked this

   Other agents commonly added to public water supplies, such as fluoride and sodium hydroxide, were not used by

   The fact that none of the municipalities used fluoride or sodium hydroxide does not bear on the bacterial-contamination difference. Both groups equally lack those agents, so they cannot explain the gap.

   2%
5. E

   Correct89% picked this

   Municipalities that do not chlorinate their water supplies are subject to stricter regulation by the regional government in regard to pipes and water tanks

   Why this is right

   This resolves the paradox precisely. The stimulus tells us contamination comes from flaws in pipes and storage tanks. If non-chlorinating municipalities are held to stricter pipe and tank regulations than chlorinators, then their water gets cleaner at the source of contamination — preventing bacteria from entering the system in the first place. That advantage in infrastructure quality more than compensates for not using chlorine, so they end up with less bacterial contamination overall. Both facts now coexist comfortably.

   Skill tested: Paradox · how this choice captures the argument's function is the move to repeat next time.

   89%