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## #22 - No chordates are tracheophytes, and all members of

jailenea
• Posts: 13
• Joined: Aug 30, 2021
#98327
Hello, can someone please explain why A is incorrect? I'm not quite understanding the initial reasoning for ruling A out.
Rachael Wilkenfeld
• PowerScore Staff
• Posts: 1158
• Joined: Dec 15, 2011
#98564
Hi jailena,

Here's the stimulus:

C = chordates
T = tracheophytes
P = member of Pteropsida
H = member of family Hominidae

Premise: C T
Premise: P T
(Inference: P C)

Conclusion P H

In order to draw a conclusion that P H, we need to find something that puts H in a category that would rule out P. Our inference above that P C means that if all H are C, P's cannot be H.

Answer choice (A) is something we can't draw that conclusion from because we end up with two premises that don't connect. We'd have P T and H T, but you cannot connect P and H in that scenario. Structurally, you can't connect the two sufficient conditions even if they have the same necessary condition.

All dogs are animals. D A
All cats are animals. C A

We can't connect dogs and cats there. We don't know if all dogs are cats, some dogs are cats, or no dogs are cats. There isn't a way to connect that chain. It's the same structural chain in answer choice (A).

Hope that helps!

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