Assumption question

In recent years, a village outside Osaka, Japan has taken to hosting a ninja festival, a celebration of Japan's heritage that reflects on its feudal past while exalting its pop culture driven present. But clearly only children take this festival seriously, for they are the only attendees who bother to dress up as ninjas.

Which of the following is an assumption on which the argument depends?

A.) Any attendee who dresses up as a ninja takes the festival seriously.
B.) No attendee who takes the festival seriously would fail to dress up as a ninja.
C.) Anyone who is not dressed up as a ninja is not attending the festival.
D.) The festival organizers have instituted a ninja-themed dress code.
E.) If an attendee is not dressed as a ninja, then that attendee will not be taken seriously by other attendees.

If confused between A or B, is there an opportunity to use the Assumption Negation Technique? How would it be applied to these answer choices? Thanks!

Answer choice A is, in essence, saying that all attendees who dress up as ninjas take the festival seriously. So the negation could be "NOT all attendees who dress up as ninjas take the festival seriously." Now we need to ask ourselves if this would undermine the argument. And the answer is: not really. Imagine that there are 100 children dressed as ninjas. 90 of them take the festival seriously, and 10 are sulking in the corner, wishing they were someplace else. In order to undermine the argument, it has to be the case that someone who isn't a child (or didn't dress as a ninja) takes the festival seriously, but it's still possible that those 90 kids dressed as ninjas are the only ones who take the festival seriously. There's no reason to believe that there's an adult somewhere, (or someone not dressed as a ninja,) who takes this festival seriously.

B says that no attendee who takes the festival seriously would fail to dress up as a ninja. The negation would be "SOME attendees who take the festival seriously would fail to dress as a ninja." But the argument posits that ONLY attendees who bother to dress up as ninjas take the festival seriously! In this case, the negation of the answer choice undermines the argument, so this is the correct answer.

infiniti007 wrote:In recent years, a village outside Osaka, Japan has taken to hosting a ninja festival, a celebration of Japan's heritage that reflects on its feudal past while exalting its pop culture driven present. But clearly only children take this festival seriously, for they are the only attendees who bother to dress up as ninjas.

Which of the following is an assumption on which the argument depends?

A.) Any attendee who dresses up as a ninja takes the festival seriously.
B.) No attendee who takes the festival seriously would fail to dress up as a ninja.
C.) Anyone who is not dressed up as a ninja is not attending the festival.
D.) The festival organizers have instituted a ninja-themed dress code.
E.) If an attendee is not dressed as a ninja, then that attendee will not be taken seriously by other attendees.

Premise: Only children dress up as ninjas.
Conclusion: Children are the only attendees who take the festival seriously.

Apply the NEGATION test.
When the correct answer choice is negated, the conclusion will be invalidated.
Answer choice B, negated:
Some attendees who takes the festival seriously fail to dress up as ninjas.
If the negation of B is true, then the argument cannot conclude that children dressed up as ninjas are the ONLY attendees who take the festival seriously.
Since the negation of B trashes the conclusion, B is the correct assumption: WHAT MUST BE TRUE for the conclusion to be valid.

The correct answer is B.

A, negated:
Not every attendee who dresses up as a ninja takes the festival seriously.
Here, it is still possible that the children dressed as ninjas are the only attendees who take the festival seriously.
Since the negation of A does not invalidate the conclusion, eliminate A.