GMAT Critical Reasoning (CR) | Re: A newly discovered painting seems to be the work of

I think that A is not the perfect answer.
Even if we negate the statement and say that "The frame was made from wood NOT local to the region where the picture was painted", there is still possibility that Drechen painted the picture in some other region. To support the conclusion we need another assumption like "Drechen didn't paint any picture outside northern Germany".