C, D and E seem defendable to me.
C: indeed, if forgery could perfectly duplicate the contour and hatching styles of a famous artist, then this would contradict the fact advanced in the passage that differences in contour and hatching styles can be used to tell forgeries apart from works of famous artists. Perhaps the "CAN" in the passage implies that this is not always possible?
D. If the painting formerly attributed to Michelangelo was attributed to Clovio (as the passage states), then its contours and hatching must be of a style similar to the style found other other works of Clovio. Perhaps it is wrong to generalize to ALL of his paintings. This could be a flaw I suppose.
E. This is in line with the assumption in the passage that the works of the two artists were told apart because their styles were different. And if they were not different, it would be impossible to tell them apart!
Hmm....
Thanks in advance!