P: Y–some–ZP: ?C: A–some–Z

Mehran April 16, 2018

Hi @sharpen7, thank you for your post.

The answer choice (E) has a detailed explanation.

You are given a premise (Y-some-Z) and a conclusion (A-some-Z). You need to find a missing premise to connect Y and A (notice that the given premise and the conclusion both have Z in common already).

This alone allows you to eliminate (A) and (B).

Now, let's consider (E): not A ==> not Y.
The contrapositive is Y ==> A

You can connect this with the flip of the given premise:
Y-some-Z
Z-some-Y==>A

Therefore: Z-some-A, which can be flipped as
A-some-Z, the given conclusion.

Hope this helps! Please let us know if you have any additional questions.

reicherjon December 31, 2019

I would love some further insight as to why D isn't correct.

I understood it as:
A - > Y -some z
Therefore
A some z
*and since some statements are reversible,
Z some A.

Please let me know, thanks!

Victorrodrigues01 January 18, 2020

yes, please elaborate on why answer choice D is incorrect. Thanks!