As I see it, jwooon, the first problem with answer A is that the second premise is not a conditional statement. When the author says "the paintings to be auctioned next week are by a wide variety of artists," there is no element of "if this, then that." It's just an absolute fact - there is a wide variety. Conditional statements aren't absolute like that; the necessary condition is only guaranteed when a sufficient condition occurs. But there doesn't seem to be a sufficient condition in that statement, and there doesn't seem to be anything necessary, either.
To show you why that isn't conditional, let's take your diagram of A
WV and put it back into words:
If a painting is in the auction next week, it is by a wide variety of artists.
Is that what they meant? Probably not. Wouldn't it make more sense if each painting was by a single artist, but that there are a lot of different artists with paintings in the auction?
Aside from that, answer A doesn't match the stimulus because the conclusion is not a contrapositive.
Finally, in your diagram, the "A" ultimately ends up meaning two different things. In the first premise, it means "included in the auction," while in the second premise, it means the auction as a whole, not just something that is in the group.
Also, it may be worth noting that "Huang Collection" does not imply a single painter. Huang might be the owner of the collection, and there could be multiple artists in that collection.
Adam M. Tyson
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