OA: C

richachampion wrote:Snowmaking machines work by spraying a mist that freezes immediately on contact with cold air. Because the sudden freezing kills bacteria, QuickFreeze is planning to market a wastewater purification system that works on the same principle. The process works only when temperatures are cold, however, so municipalities using it will still need to maintain a conventional system.

Which of the following, if true, provides the strongest grounds for a prediction that municipalities will buy QuickFreeze's purification system despite the need to maintain a conventional purification system as well?

(A) Bacteria are not the only impurities that must be removed from wastewater.
(B) Many municipalities have old wastewater purification systems that need to be replaced.
(C) Conventional wastewater purification systems have not been fully successful in killing bacteria at cold temperatures.
(D) During times of warm weather, when it is not in use, QuickFreeze's purification system requires relatively little maintenance.
(E) Places where the winters are cold rarely have a problem of water shortage.

Prediction: Municipalities will buy QuickFreeze system despite needing to maintain conventional system.
Premise: QuickFreeze's technology only works when temp is cold.

We're trying to bolster the claim that it makes sense to buy the QuickFreeze system. Imagine you're in charge of water purification for the town. You're considering buying QuickFreeze even though it only works when it's cold, and you'll have to hang on to your old system. Well, this course of action would only make sense if the QuickFreeze system provides some benefit beyond what you get from your old system, right? In other words, if the old system was already killing bacteria well when it was cold, there'd be absolutely no need for the QuickFreeze system as killing bacteria when it's cold is the only thing this system does. This is what's captured in C.

C negated: Conventional wastewater purification systems have been fully successful in killing bacteria at cold temperatures.
Well, if the old system has been fully successful killing bacteria in the cold, there'd be no need to buy the new model, thus undermining the plan. If you have a strengthen question, the negation of the answer choice should undermine the conclusion. So we know we've got our answer.