This is GMATPill
Framework #8 Inference.
The question stem that tells us this is an "inference" question is "...can be logically concluded..."
So actually you might not necessarily use negation here -- negation is used to find an answer choice that SUPPORTS the argument presented in the passage.
Here, we are actually doing something different. We are finding an answer choice that is SUPPORTED BY information in the passage.
What is some of that supporting information? Well the last sentence says forgers cannot hope to be able to replicate all aspects of a pro master artist. Well...if that's true...if they can't fully replicate a pro artist...and the computer program can detect *all* aspects....then the computer program can detect a fraud when it sees a forgery that does not score fully in all criteria. So that's why information in the passage supports C.
The reasoning presented via negation is not something you want to follow for an inference question...you should be looking at it using the gmatpill
... and more
What's Inside GMAT Pill?
Zeke Lee, GMAT Pill Study Method (Study Less. Score More.)
GMAT Pill Reviews | GMAT PILL Free Practice Test