In 1563, in Florence' s Palazzo Vecchio, Giorgio Vasari built in front of an existing wall a new wall on which he painted a mural. Investigators recently discovered a gap between Vasari' s wall and the original, large enough to have preserved anything painted on the original. Historians believe that Leonardo da Vinci had painted, but left unfinished, a mural on the original wall; some historians had also believed that by 1563 the mural had been destroyed. However, it is known that in the late 1560s, when renovating another building, Santa MariaNovella, Vasari built a facade over its frescoes, and the frescoes were thereby preserved. Thus, Leonardo' s Palazzo Vecchio mural probably still exists behind Vasari' s wall. Which of the following is an assumption on which the argument depends?
A: When Vasari preserved the frescoes of Santa Maria Novella he did so secretly.
B: Vasari probably would not have built the Palazzo Vecchio wall with a gap behind it except to preserve something behind the new wall.
C: Leonardo would probably have completed the Palazzo Vecchio mural if he had had the opportunity to do so.
D: Leonardo rarely if ever destroyed artworks that he left unfinished.
Choose A, B, C or D as your solution.
B