Although water in deep aquifers does not contain disease-causing bacte

Question

Competition Mode Question

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 chlorinated had less bacterial contamination than the water supplied by the municipalities that added chlorine.

Which one of the following can properly be concluded from the information given above?

(A) A municipality’s initial decision whether or not to use chlorine is based on the amount of bacterial contamination in the water source.

(B) Water in deep aquifers does not contain any bacteria of any kind.

(C) Where accessible, deep aquifers are the best choice as a source for a municipal water supply.

(D) The regional government’s standards allow some bacteria in municipal water supplies.

(E) Chlorine is the least effective disinfecting agent.

eakabuah · Answer

D is the right answer.

The best way to answer this question is by eliminating the wrong answers based on the information provided above.

This cannot be properly concluded from the information provided above. Why? Because it is clearly stated that the water source, deep aquifers, does not contain disease-causing bacteria and that chlorine is used as a disinfectant because contamination can occur as a result of flaws in pipes or storage tanks. In any case, the 30 municipalities that use chlorine rather had more bacteria in the water than the 20 that does not use chlorine. This implies that the bacteria impurities are more predominant in the pipes and tanks of the 30 that use chlorine that the 20 that don't. A can be eliminated.

Wrong inference. It is clearly stated in the information above that water in deep aquifer does not contain disease-causing bacteria. That does not mean that other bacteria such as useful and harmless bacteria are not present in water in deep aquifers. B can be eliminated.

Wrong conclusion from the information provided above. The information above only talks about water in aquifers. No other water source of water is compared with the water in aquifers. There could be other sources that are better than aquifers as source of water or aquifers can also be the best source of water. We are unable to make this comparison based on the information provided above. C can be eliminated.

This is correct. Why? If the municipal water supplies does not allow any form of bacteria in the municipal water supplies, one would expect that they would ensure that there is no bacteria in the water that the water supplied by the 50 municipalities not to contain any bacteria. On the contrary, the 30 municipalities whose water is chlorinated rather contains a higher bacteria than the 20 that did use chlorine. Obviously, the municipalities allow for some level of bacteria in the water supplies.

This cannot be correctly concluded based on the information above. First of all, chlorine is not compared with any other disinfecting agent in the information above. Secondly, we are not made aware of the amount of chlorine added to the water supply system and the corresponding level of purification we should anticipate. E can be eliminated.

exc4libur · Answer

ARGUMENT
  deep water does not contain disease bacteria;
  some water suppliers added chlorine and some did not;
  all passed contamination standards;
  those that did not had less bacterial contamination;
  so these had less bacteria in their pipes and/or tanks.

Ans (D) all passed standards, and without chlorine had less bacteria - thus standards allows some bacteria.

unraveled · Answer

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 chlorinated had less bacterial contamination than the water supplied by the municipalities that added chlorine.

Which one of the following can properly be concluded from the information given above?

(A) A municipality’s initial decision whether or not to use chlorine is based on the amount of bacterial contamination in the water source. - WRONG. Does not goes well the argument. We can't be sure.

(B) Water in deep aquifers does not contain any bacteria of any kind. - WRONG. Not mentioned neither we can infer. Also its pretty big claim.

(C) Where accessible, deep aquifers are the best choice as a source for a municipal water supply. - WRONG. Similar type of error as in option B.

(D) The regional government’s standards allow some bacteria in municipal water supplies. - CORRECT. Thus the non chlorinated water has some bacteria present in it.

(E) Chlorine is the least effective disinfecting agent. - WRONG. Same error as option B and C.

IMO Answer D.

shameekv1989 · Answer

Isn't mentioned anywhere in the passage

- Water in deep aquifers do not contain only disease causing bacterias - It may contain other kinds of bacteria

Isn't mentioned about whether its best or worst

Correct - as is evident from "The water in all of the municipalities met the regional government’s standards for cleanliness" and "because contamination can occur as a result of flaws in pipes or storage tanks". The two statements imply that contamination is certainly there but it is contained by the government's standards for cleanliness.

Least effective or most effective isn't mentioned in the passage

Answer - D

jrk23 · Answer

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 chlorinated had less bacterial contamination than the water supplied by the municipalities that added chlorine.

Which one of the following can properly be concluded from the information given above?

(A) A municipality’s initial decision whether or not to use chlorine is based on the amount of bacterial contamination in the water source.

(B) Water in deep aquifers does not contain any bacteria of any kind.

(C) Where accessible, deep aquifers are the best choice as a source for a municipal water supply.

(D) The regional government’s standards allow some bacteria in municipal water supplies.

(E) Chlorine is the least effective disinfecting agent.

B- Don't contain any bacteria is wrong, can't say
C-the word" the best choice" make it irrelevant
d-nowhere mentioned this.
E- we can't say anything about chlorine

i think than its "a"

madgmat2019 · Answer

(A) A municipality’s initial decision whether or not to use chlorine is based on the amount of bacterial contamination in the water source.......the amount of bacteria before using chlorine is not discussed.....INCORRECT

(B) Water in deep aquifers does not contain any bacteria of any kind.,.....INCORRECT....because it do contain bacteria.

(C) Where accessible, deep aquifers are the best choice as a source for a municipal water supply.......from the given info we cannot say that its the best,....which is an extreme conclusion.....INCORRECT

(D) The regional government’s standards allow some bacteria in municipal water supplies.......Yes....because the water do consists of bacteria ......CORRECT

(E) Chlorine is the least effective disinfecting agent........TOO EXTREME.....INCORRECT

OA:D

PRIYANSHU1111 · Answer

GMATNinja  How do we choose between A and D?

gentvenus · Answer

(A) Incorrect as the amount of bacteria before chlorine is used is not discussed.
(B) Incorrect as water in deep aquifers clearly do contain bacteria.
(C) Incorrect as saying its the best is an extreme conclusion.
(D) Correct as water is very likely to consist of bacteria.
(E) Incorrect as saying chlorine is the least effective is an extreme conclusion.

VerbalBot · Answer

Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.

Although water in deep aquifers does not contain disease-causing bacte

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Critical Reasoning (CR) Questions

Although water in deep aquifers does not contain disease-causing bacte

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards