Sufficient & Necessary Questions - - Question 30

Anatomical bilateral symmetry is a common trait. It follows, therefore, that it confers survival advantages on organ...

kristinsmith04 December 16, 2019

Why doesn't it matter that the correct answer choice doesn't also begin with a statement of fact?

I originally included the bilateral symmetry piece as a diagrammed portion so I was waiting for the answer choice to have a statement of fact that leads to the middle premise, which leads to the conclusion. See below for what I mean: First, stimulus tells us ABS > CT > SA. Then, the stimulus tells us, Not SA > Not CT. So, it goes, A> B > C, thus, Not C > Not B Should I just NOT diagram factual statements like Anatomical Biological symmetry is a common trait unless it uses Suff/Nec terms like If ABS, then that person possesses a common trait Thx!

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BenMingov December 18, 2019

Hi Kristin, thanks for bringing this question up!

I must admit that this question kind of got me. It actually seems to be a really odd way of just making a conditional statement and concluding the contrapositive.

Reasoning: NOT Bilateral symmetry confer advantages - > NOT common
Conclusion: Common - > Bilateral symmetry confer advantages

Answer choice C is paralleling the original argument because it too is just concluding the contrapositive of its reasoning.

It turns out the statement of fact at the beginning was the argument triggering the sufficient condition.

I hope this helps, please let me know if you have any other questions!