I'm not a tutor, but I think I can help.
Concerning C: it is wrong because if it was common (double negative, not uncommon equates to common) to use live models, then C potentially strengthens rather than weakens. Remember that according to the stimulus the artist had a self-portrait, meaning he used himself as a live model. If C is true, then it is possible for the artist to have again used himself as a model, like in the self-portrait to paint himself in the scene of the battle picture.
B is easier to eliminate, although it does not strengthen, because it is simply irrelevant. B does NOT pass the "so what-" test?
Anyway I don't know if this helps, but I thought I'll give it a try!
Respectfully,
Mazen
Emil-Kunkinon August 14, 2022
Hi Mazen,
I broadly agree, although I think we can additionally eliminate C on the grounds that it suggested that someone else painted the painting, and that the artist was sitting as a model.