In order to cut down on construction costs, the building

the answer is E because D talks about the similarity and being similar is not equal to being same . This is in fact GMAT one of the traps in the CR answer choices

One big lesson you can take away from this problem is in its basic structure. Look at how broad the conclusion is ("Thus there is no safety risk") vs. the specificity of the contractor's premise (specific to the load that this new sealant can withstand). The gap in the argument is huge: what if there are other safety risks inherent in the new sealant besides just the amount of load the sealant can withstand?!

That's where (D) comes in - what if it can withstand that load, but not for a very long time. The longevity of the sealant would then pose a safety threat. Note the main role of (D), which is to protect against "other safety threats." The argument is basically assuming that as long as a sealant could handle the weight load, there are no safety issues; the correct answer structure here is just bringing up another possible safety threat and saying "that's not a problem" - by ruling out other potential weaknesses, the right answer helps protect the argument.

(Sidenote: if it were me writing this question based on the prompt given, I'd have a hard time resisting the fact that the premise says "and no residential building has that kind of load" - another HUGE assumption here is that we're even talking about a residential building. The GMAT loves that extra, seemingly-unimportant modifier or adjective in a major premise that makes it really specific, coupled with like I mentioned above a really broad conclusion. Just something else to look for on these - when the conclusion is broad, the gap in logic often lies in how narrowly drawn the main premise is.)

I am confused between B, C and D. They all sound the same to me ie B and D compare the two materials and portray the strength of the second material and D talks about the new materials strength in general.

Hi

Let me try to address your query. Options (B), (C) and (D) talk about different things with respect to the stimulus.

Option (B): The alternative material has the same chemical and physical characteristics as those of the originally proposed sealant. This talks about the overall physical properties of the new material and states that these are the same as the original sealant.

Option (C): Buildings built with the alternative material have been found to be safe in a recent audit performed by the state government. This option does not really talk about the material as such, but talks about the resulting buildings which have used the alternative material. It states that these buildings are safe, but does not compare the safety with the buildings using the original sealant.

Option (D): The strength of the proposed alternative has similar longevity as that of the originally proposed sealant. This is the only option which compares the two materials, and states that the longevity ie; the amount of time for which the alternative material retains its strength is the same as that of the original sealant.

As you can see, each of these options talks about different aspects of the conclusion. Since the argument is about using the new material, we need an answer option that compares the two materials, and more specifically, compares the new material favourably with the original sealant. Only answer option (D) does this and hence is the correct answer.

Hope this clarifies.

Some one who has done chemical engineering and has been working in construction chemical company will always prefer B over D. It must be assumed physical and chemical properties same other wise argument falls. It's a faulty question.

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Hi everyone. I cannot understand why C is incorrect. It clearly supports the conclusion with the audit proof. It makes conclusion and the whole argument strong. Please someone explain elaborately why C is incorrect. Thanks in advance.

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Let's focus on the conclusion:
"There is no safety risk (in using the new material), because the new material can withstand up to 10 tonnes of load per story, and no residential building has taken that kind of load".
So the constructor is basically saying that because it can withstand more load than a residential building has ever faced, it is not risky to use.
The question is asking us to find an assumption that the constructor has based his argument on.

Option C discusses government audits of buildings constructed by using the material. Nowhere in the passage does the constructor ever use an audit, or a government support, or anything similar to support his argument. His argument is simply that, it can withstand more load than necessary, so it is safe. So, C is out because it is not relevant to the passage. If you are not convinced, try negating C: "Buildings built with the alternative material have been found unsafe in recent audits". While it may seem to weaken the authors argument, it requires an extra step - it requires that the buildings that were audited were deemed unsafe because of the alternative material. However, there is no information to give us that extra assumption. The buildings could have been unsafe because of the terrain they were built on, weather, bad building practices unrelated to the sealant, etc. So, while C may seem relevant to the argument, C requires further assumptions to be impactful.

Now lets focus on D.
D is very relevant - imagine the material could withstand more load than needed, but it is only durable for 2 hours. Is it really logical to say that there is no safety risk? Of course not, because then the building would collapse in 2 hours. So the constructor has made the assumption that the two materials have similar longevity. If you try to negate D, as I did above, the entire argument makes no sense - no further assumption needed unlike C.

Hope this helps!

What you're saying is true, but the question is asking something else. It is asking what does the contractor's 'PROPOSAL' assume. The contractor is saying that buildings built with the new alternative material can withstand up to ten tonnes of load per story and no residential building has that kind of load. Thus, on that basis, there is no safety risk.

D says The strength of the proposed alternative has similar longevity as that of the originally proposed sealant. If you negate this option, the alternative will not have similar longevity as the original sealant, then his proposal won't work. So D is the answer.