C

@tomgbean, There are a couple of issues with (C). First, the conclusion is conditional, whereas in the stimulus ~ A & ~ B is one of the premises, and second, it talks about a vaccine in general not a specific vaccine or a specific computer as in the stimulus, i.e. commonly used vaccine or intelligent computer. The argument discusses specific attributes of a variable with a certain characteristic, i.e. intelligent computer possesses X Y Z whereas (C) talks about a general concept - any vaccine. The original argument can be diagrammed as: I -> C v S v L ~ C & ~ S I > C versus (C) V -> D v A v P ~D & ~ A -> P Let me know if you have any other questions.