Here is what the argument says:

- Washing machines are teeming with bacteria that can cause infections.
- Rinsing these machines with bleach (note that it doesn't say concentrated bleach/diluted bleach and doesn't talk about the amount of bleach to be added) gets rid of such bacteria.
- However concentrated bleach can severely corrode the metal drum in the machines.

Conclusion: Thus, diluted bleach is an effective and safe means of eliminating any health risks from such washing machines.

There are various questions that can be raised to weaken the conclusion.
At what level of dilution is the bleach effective and safe?
Is bacteria the only health risk in the washing machines?
Does the beach itself leave deposits in the machine and create health risks?

Option (A) says that the machines have many other pathogens. We don't know whether the bleach is effective on them or not. Hence, we cannot say that bleach will eliminate all health risks. Hence it weakens the conclusion.

B. Undiluted bleach is not more powerful than diluted bleach in killing bacteria.
It tells us that diluted bleach is effective (and safe). Hence it strengthens our conclusion.

C. Many companies come with gentle bleach blends that do not corrode the metal drum of the household washing machines.
Irrelevant. It tells us that suitably diluted bleach is available.

D. Various studies have shown that certain bacteria can live outside the human body for long periods of time on various objects such as clothes, toys etc.
Gives more information about the first sentence of the argument. Has no connection to the conclusion that bleach is effective in eliminating all health risks.

E. Most household washing machines come with a hot-water cycle that is set at a temperature of 90 degrees Celsius, a temperature that has been cited as ideal for killing various disease-causing bugs in these machines.
Gives another method of eliminating health risks. Does not weaken that bleach in effective in eliminating health risks.

Answer (A)
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Between C & E I chose E.

Awaiting OA.

Rgds,
Dhruva

A (IMHO) the argument says "effective means of eliminating any health risks from such washing machines", not just bacteria, so even when you kill bacteria with wtvr bleach you use, health is still endangered by other harmful means aka pathogens.

narmadadhruv

Choice E deals with bugs, not bacteria... aren´t you assuming they both pose the same threat?

Regards,

A for me.

Conclusion states that "as long as it is diluted properly, is an effective means of eliminating any health risks from such washing machines, with no harmful effects on these machines"

Since A states that there are other pathogens in machines, this weakens the claim.

Hence answer is A

Thanks for pointing that out! But the other in option A troubles me.

Regards,
Dhruva

Hi,
the catch word is OTHER.. this means there are various other pathogens other than bacteria that can cause diseases..
However the argument shifts the focus from bacteria to no health risks atall
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This is very comprehensive, but I think that your questions will be answered, so please bear with me.

A. Studies have shown that besides bacteria, many other kinds of pathogens can be found in regularly used washing-machines.

Within scope - "any health risks" is the conclusion drawn by the author. Such a generalization would find weakness by introducing health risks other than that caused by bacteria. Do we know that bleach kills these other pathogens? Since we must take this answer choice as true, it brings considerable doubt and/or questions to whether bleach can eliminate any health risks, and the author's conclusion is hasty and insufficiently supported.

This is the answer.


B. Undiluted bleach is not more powerful than diluted bleach in killing bacteria.

This may sound as if it weakens, but it's irrelevant. It may require the author to modify the conclusion to say that either diluted or undiluted bleach will be effective in killing bacteria... in fact, I argue that the author doesn't even have to modify the conclusion, as the author only makes a claim in the conclusion with respect to diluted bleach (yes, the argument brings up details about undiluted bleach causing damage to washing machine drums, but the conclusion is about how extreme that info is interpreted - e.g. restate the conclusion "only with respect to diluted bleach, we can conclude X").

Anyway, the point still remains that undiluted bleach will still cause damage to the machine. Thus, you'd still want to use diluted bleach instead of undiluted bleach, as the author suggests.

C. Many companies come with gentle bleach blends that do not corrode the metal drum of the household washing machines.

This actually strengthens the author's argument. It's similar to restating the info that's already mentioned, as gentle bleach blends is a type of diluted bleach. It's not irrelevant - if undiluted bleach seriously damages washing machine drums, then diluted bleach's effects on washing machine drums cannot be inferred. So, the author makes a leap in concluding that diluted bleach is safe for machines.

Also, as a very minor aside, if diluted bleach wasn't available (e.g. "there are no bleach blends..."), it would be equivalent to suggesting a magical solution, as if-then logic dictates that any false hypothetical can be followed by a true or false conclusion, making the entire logical equation true (e.g. if it rains chocolate outside everyday, then I am a billionaire = true statement)! Then it seriously undermines the author's conclusion because blends or diluted bleach may not be available for purchase for use in washing machines, making the author's solution ineffective and entirely irrelevant. Thus, with the wording changed, choice C would be the answer, as bleach cannot be used to kill any bacteria, and will knock out the actual answer to this question, which at least kills some bacteria even if more pathogens are introduced (unavailable bleach effectively eliminates no health risks vs., bleach eliminates some or possibly even all health risks, respectively).

D. Various studies have shown that certain bacteria can live outside the human body for long periods of time on various objects such as clothes, toys etc.

This only adds to the given info with very little value-added. This answer choice reinforces the background detail to generate more support for the author's conclusion. Conclusion: Use diluted bleach... Author's support: because washing machines transfer bacteria onto clothes, which... Answer Choice D: "Various studies have shown that certain bacteria can live outside the human body for long periods of time on various objects such as clothes, toys etc."...

E. Most household washing machines come with a hot-water cycle that is set at a temperature of 90 degrees Celsius, a temperature that has been cited as ideal for killing various disease-causing bugs in these machines.

This may sound as if bleach is unnecessary, but the point still remains... if the hot-water cycle is sufficient at killing various disease-causing bugs, which is indeed a health risk, then are other disease causing sources eliminated? It's confined to just disease-causing bugs and does not necessarily pertain to bacteria, or any other health risks for that matter. In fact, it can be used to support the conclusion, in that the hot-water cycle can combine with the diluted bleach to eliminate (more, not necessary any and all) health risks. Does it weaken or support the author's conclusion? Clearly, this answer choice has commitment issues.

Mechmeera

Look at my explanation on the first link. Conclusion says ANY, and A attacks exactly this particular word by telling you that you are still endangered, and the conclusion that you are safe is no longer there.

As for B - it is tricky indeed. Say the answer was written as follows " Undiluted bleach is just as powerful than diluted bleach in killing bacteria." This is the same as saying that both types of bleach have the same power, and that diluted isn´t more or less powerful. Now, would that weaken your argument? Or would it is still be valid to argue that using diluted bleach would eliminate health risks, just as undiluted would do so?
Thus, this does not weaken the argument. (Had the answer been "Undiluted bleach is MORE powerful than diluted bleach", you would have a weakener as well. But that´s not the case.)

Hope it helps.

best

strongly feel that I have seen this question before. Anyways, some of the options are too far fetched and hence easy to eliminate.
Hope I will improve in the next 2 months.

[quote="souvik101990"]

Studies have shown that regularly used household washing machines are teeming with bacteria that find their way onto our clothes and consequently onto us, causing various bacterial infections. Rinsing these machines with bleach is an effective way to get rid of such bacteria. However, certain other studies have shown that bleach, when used in the undiluted form, can severely corrode the metal drum in the machines. Thus, bleach, as long as it is diluted properly, is an effective means of eliminating any health risks from such washing machines, with no harmful effects on these machines.

The key is which option weakens the crux of the argument 'means of eliminating any health risks from such washing machines'

A. Studies have shown that besides bacteria, many other kinds of pathogens can be found in regularly used washing-machines.
- this surely seem to weaken the argument, as pathogens can eliminate health risks. but we dont know for sure if pathogens can cause health risk but we have to assume them on the same lines as bacteria. this is a better option, but have to rule out all other options.

B. Undiluted bleach is not more powerful than diluted bleach in killing bacteria.
- in other words diluted beach helps. so only strengthens the argument.

C. Many companies come with gentle bleach blends that do not corrode the metal drum of the household washing machines.
- this does not weaken the argument

D. Various studies have shown that certain bacteria can live outside the human body for long periods of time on various objects such as clothes, toys etc.
- not relevant

E. Most household washing machines come with a hot-water cycle that is set at a temperature of 90 degrees Celsius, a temperature that has been cited as ideal for killing various disease-causing bugs in these machines.
- this strengthens the argument in a lot of way unless you have noticed 'bugs' and not bacteria.

So considering these, seems to be the better option of all.

bleach, as long as it is diluted properly, is an effective means of eliminating any health risks from such washing machines, with no harmful effects on these machines

Marked above is the conclusion, given this, any option that suggests that
1.) diluted bleach does not corrode
2.) diluted bleach does kill all harmful bacteria should strengthen the arg.; negation of which shall weaken it.

A.->talks about another entity; even if we were to consider this option, we are assuming that pathogens are harmful.
B.-> strengthens
c. -> Close to pre-thinking options (mentioned above)
D.-> strengthens
E.-> somewhat like A; in that it introduces another entity.

Rgds,
Dhruva

Studies have shown that regularly used household washing machines are teeming with bacteria that find their way onto our clothes and consequently onto us, causing various bacterial infections. Rinsing these machines with bleach is an effective way to get rid of such bacteria. However, certain other studies have shown that bleach, when used in the undiluted form, can severely corrode the metal drum in the machines. Thus, bleach, as long as it is diluted properly, is an effective means of eliminating any health risks from such washing machines, with no harmful effects on these machines.

Which of the following, if true, weakens the argument above?

A. Studies have shown that besides bacteria, many other kinds of pathogens can be found in regularly used washing-machines.

B. Undiluted bleach is not more powerful than diluted bleach in killing bacteria.

C. Many companies come with gentle bleach blends that do not corrode the metal drum of the household washing machines.

D. Various studies have shown that certain bacteria can live outside the human body for long periods of time on various objects such as clothes, toys etc.

E. Most household washing machines come with a hot-water cycle that is set at a temperature of 90 degrees Celsius, a temperature that has been cited as ideal for killing various disease-causing bugs in these machines.

How I did was

bleach, as long as it is diluted properly, is an effective means of eliminating any health risks from such washing machines, with no harmful effects on these machines

None of answer choices talk about effects on machines. have to check for means of eliminating health risks

Studies have shown that regularly used household washing machines are teeming with bacteria that find their way onto our clothes and consequently onto us, causing various bacterial infections. Rinsing these machines with bleach is an effective way to get rid of such bacteria. However, certain other studies have shown that bleach, when used in the undiluted form, can severely corrode the metal drum in the machines. Thus, bleach, as long as it is diluted properly, is an effective means of eliminating any health risks from such washing machines, with no harmful effects on these machines.

Which of the following, if true, weakens the argument above?

Scope Shift: The argument talks about bacteria and its health threats, but concludes about 'any health risks'. We need to expose this.

A. Studies have shown that besides bacteria, many other kinds of pathogens can be found in regularly used washing-machines. - Perfect.

B. Undiluted bleach is not more powerful than diluted bleach in killing bacteria.

C. Many companies come with gentle bleach blends that do not corrode the metal drum of the household washing machines.

D. Various studies have shown that certain bacteria can live outside the human body for long periods of time on various objects such as clothes, toys etc.

E. Most household washing machines come with a hot-water cycle that is set at a temperature of 90 degrees Celsius, a temperature that has been cited as ideal for killing various disease-causing bugs in these machines.

Binit.

It is essentially the same thing. When they ask you to strengthen the argument, they are asking you to strengthen the conclusion. Look, anyway, you have to take premises to be true. So you can't strengthen/weaken them. The only thing you can strengthen/weaken is the conclusion because that is the author's opinion.

So "strengthen the conclusion" and "strengthen the argument" are the same things.
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Argument Analysis - Bacteria is a health hazard
Rinsing with bleach can help get rid of this bacteria.
Undiluted bleach can be harmful for the Machines.
Conclusion : Rinsing the machine with diluted bleach is the way to do it since it will kill the bacteria and will not harm the machine.

Pre-Thinking : Lets break the conclusion. We have to think of scenarios in which rinsing with diluted bleach will not have the aforementioned effects.
1 - Diluted bleach is not as good as Undiluted Bleach in killing bacteria.
2- There are things ( Other than bacteria ) inside the machines that even bleach can not kill.

Answer choice review :

A - I do not care what happens outside the machine ( Incorrect )
B - As effective as - So Diluted Bleach is either equally effective or more effective than Undiluted bleach. (Sounds like a strengthener; Incorrect)
C - Irrelevant
D - In line with our pre-thinking, therefore correct
E - No one is worried about the cost( Incorrect )
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