Passage Summary: Zachary wants to restore the Sistine Chapel by removing all paint that isn't part of the original wet-plaster fresco, assuming anything else was added by later people. Stephen notes that artists back then often added their own finishing touches after the frescos dried.

Conclusion: Stephen implies that Zachary’s plan to strip away everything but the original fresco might inadvertently destroy parts of Michelangelo's intended work.

Reasoning: Stephen points out that it was a common practice for artists during Michelangelo's time to add their own painted details to a fresco after the plaster had already dried.

Analysis: This is a Method of Reasoning question, so we must focus on the structural role of Stephen's contribution. Stephen introduces a historical fact that complicates Zachary’s definition of 'original work.' By noting that the artist himself likely added non-fresco elements, Stephen suggests that Zachary's criteria for restoration is too narrow. Look for an answer that describes Stephen as providing information that calls into question the adequacy of Zachary's proposed method.