It took me 2 minutes
but I got the answer right
a. In fine lacquering, which is an ornamentation process, artisans paint natural lacquer obtained from trees on objects, allowing it to dry, and then smoothing it with a whetstone before the application of further coats. - I think this is a good choice, but for the use of "in" at the start. The modifier is trying to modify fine lacquering by use of which. But the prepositional phrase is suffixed by a noun modifier which makes the construct obscure. No pronoun ambiguity.
b. Fine lacquering is a process of ornamentation in which artisans paint objects with natural lacquer obtained from trees, allow it to dry, and then smooth it with a whetstone before applying further coats. - Better choice than A. The author intends to say "process of ornamentation" rather than "ornamentation process". No pronoun ambiguity.c. When fine lacquering, artisans do a process of ornamentation by painting on objects natural lacquer obtained from trees, allowing it to dry, and then smooth it with a whetstone before they apply further coats. - The adverb "when" should not be used. It implies only when this process is underway, do the artisans try some sort of ornamentation.
d. Fine lacquering is an ornamentation process in which artisans, painting natural lacquer obtained from trees on objects, allow it to dry, and then smooth it with a whetstone before they apply further coats. The author intends to say "process of ornamentation" rather than "ornamentation process". A bigger error is pronoun ambiguity at the end which uses "they". "they" does not have a clear referrent.
e. The ornamentation process of fine lacquering is one in which artisans paint natural lacquer obtained from trees on objects, allow them to dry, then smoothing it with a whetstone before applying further coats. - This suggests that you are ornamenting fine lacquering. Does not make sense.