#21 - People who object to the proposed hazardous waste

[Txflier]

I'm obviously missing something here. For answer choice C wouldn't "If it is more than 200 years old" Make it the Sufficient and "Special" the Necessary. And "If a book was set with wooden type" The sufficient and "200 years old" the Necessary? Ok Image not working so well.

Rain5 --> TreesBlossom
Rain5 --> ResFullMay1

ResNOTfullmay1 --> TreesNOT blossom. I see the wrong logic here.

C)
200--> Special
WoodenType --> 200

WoodenType --> 200 --> Special

NOT special --> NOT200 --> NOTwoodenType

and that looks ok to me.

[Steve Stein]

In this example a single sufficient condition brings about two necessary conditions:

If .5 cm of rain falls in April, then the trees blossom. And...
If .5 cm of rain falls in April, then the reservoirs get full.

This could be diagrammed as follows:



The contrapositive would be as follows:



As we can see, if the reservoirs are not full, that information tells us that there was not at least .5 cm of rain in April. But because that conditional arrow goes in only one direction, that information provides no insight into whether or not the trees blossomed--so the author's conclusion is not valid.

As you pointed out, answer choice C presents valid logic—so it cannot be the answer choice that exhibits the flaw found in the stimulus.

In correct Answer choice A, however, a single sufficient condition is presented with two necessary conditions, and the author makes the exact same mistake as that found in the stimulus.

[Txflier]

Thanks for clarifying, and oops I misread my answer sheet and was thinking C was right.

[moshei24]

Hi,

I see why all the wrong answer are right, but it's not completely clear to me why C is correct. How can that be shown as fact from the stimulus? I see how it's most likely true from the stimulus, but that's wrong in must be true question. Would you be able to explain this question to me?

Thank you,
Moshe

[Joshua Kronick]

The stimulus tells us the current location of the waste is unsafe and poses an unacceptable risk, and therefore it should be moved to this other proposed location, despite possible long-shot type concerns of the waste escaping. If the proposed location were not more safe why would they be moving it then? That would seemingly make the entire stimulus nonsensical. While I understand the desire to apply the Fact Test and make sure nothing is out of scope nor says something that could be true rather than must be true, you are allowed to use some basic common sense assumptions in your approach and this in my opinion certainly meets that.

[moshei24]

Aha - the assumption must be that it's safer or else they wouldn't suggest it in the first place. Gotcha. Thanks!

[cecilia]

This was the one on waste storage sites. I ultimately chose ( C ) but it took me a while to rule out ( E). Is E wrong because of the extreme ("any site' ) wording in the statement?

Also, was this a simply a support question or an inference ( must be true) question?

Thanks in advance....

[Jon Denning]

Hey cecilia - thanks for the question! The premises given here support the author's belief that moving the waste to the proposed new site, while not guaranteed to be perfectly safe, is still a safer plan than leaving the waste at its current site. That doesn't necessarily mean that ANY new site is better than the current site, though. All the author discusses is that (1) it shouldn't stay where it is "for many years," and (2) moving it to the proposed new site is preferable to leaving it in its current spot.

Always be careful about picking answers in Must be True that use language as strong/absolute as that in E, since it would take a lot of information to know that "ANY site is safer than the current site." That means that where it currently is is literally the absolute worst place, safety-wise, that we could put it--less safe than the ocean, or public parks, or school playgrounds, or your bathtub--and there's not nearly enough information in the stimulus to conclude anything as strong as that.

As to your final question about support vs inference (must be true), they're really the same thing. Must be True question stems sometimes use language like "which of the following must be true?," and sometimes use language seen here like "most strongly support which of the following?," but regardless you're just looking for an answer choice that follows as logically/validly as possible from the stimulus information. Just be careful not to confuse that with Strengthen, where the stem might say "which of the following most strongly supports the conclusion above?"

Hope that helps!

[cecilia]

Thanks Jon!

[jonwg5121]

Hi,

Can you please explain why answer choice (A), (B), (D) and (E) are incorrect? I chose (D). Below is my thinking process on how I eliminated some answer choices. Thank you.

(A) Stimulus does not say anything about waste should not have been stored in its current location in the first place.
(B) Opposite of what the stimulus says.
(C)?
(D)?
(E) Not necessarily true. Possible for new site to be worse than present site.