Could be false. To say that contours and hatching are the main features is too extreme. We only know that contours and hatching are some features to help distinguish works of art. It is possible there are many more features than these.

Could be false. We only know that some of these former drawings are actually Giulio Clovio’s, but we can’t assume they are forgeries. It is possible that these drawings were only mistakenly attributed to Michelangelo, and Giulio Clovio never intended to forge the drawings.

Could be false. We only know that analyzing contours and hatching helps to distinguish works between famous artists and forgeries, but we can’t assume that this analysis is foolproof.

Could be false. The stimulus does not provide us any information about Clovio’s works to infer this statement. It is possible that Clovio’s style changed over time, so Clovio may not use the same features in all of his works.

Must be true. We can infer that an analyzable difference exists because the analysis described in the stimulus did in fact help to show that some drawings formerly attributed to Michelangelo are actually by Clovio.