Solving Justify the Conclusion questions

[mistd]

So I know that when the premise and the conclusion have the same necessary condition, you need something linking the two sufficient conditions. For example:

Premise A --> B
Conclusion C --> B

Answer: C --> A

But why is it C --> A and not A --> C?

I've been trying to figure it out but I can't get the logic behind it, forcing me to rely on a mechanistic approach without knowing why I'm getting the answers correct.

Thank you in advance!

[LSAT Blog]

I explained this here:

http://lsatblog.blogspot.com/2009/10/lo ... ption.html

Does that clear it up?

[mistd]

Ah I should have looked at your blog first. Of course.
Thank you!