The best answer is D.
The context indicates that what caused the patina was years of
exposure
to smoke and heat. Lines 55–57 tell us that household tansu were rarely
finished.
Thus, B makes little sense. The context makes no mention of carving
designs,
which makes A implausible.
C is also a poor choice, since it is hard to
imagine something being described
as "lovely" if it has been destroyed.