So we are assuming/inferring that:
a. The paintings did not exhibit simple, elegant lines and vivid colors before 1886.
b. The "other culture" was Japanese.
So, simple, elegant lines were related to Japanese artistic traditions.

Except. So let's see which ones do provide SOME support:

A. Yamato-e, hmmm.. suspicious of this one. But YES.
B. Yes.
C. Yes. He may have incorporated changes from there.
D. Hmmm. now here's a strong contender.
E. Yes.

So, IMO D.

+1 D

should be D

D for me too..

+1 for D,
speaks about 1885

Art historians conclude that Vincent Van Gogh must have become interested in Japanese art in 1886, based on evidence that Van Gogh's painting style changed in a way in that year that reflected the "incorporation of another culture's artistic tradition."

The four wrong answer choices will provide some support for, or strengthen, the art historians' conclusion that Van Gogh became interested in Japanese art in 1886. The correct answer will either have no effect on the conclusion or weaken it; in other words, it will be an irrelevant piece of information or one that makes it LESS LIKELY that Van Gogh became interested in Japanese art in 1886.

Choice D is correct. If Van Gogh painted copy of a Japanese print in 1885, he must have become interested in Japanese art prior to 1886. This choice fundamentally contradicts the art historians' conclusion.

Choice A: That a typical feature of Japanese paintings appeared in Van Gogh's work in 1886, but at no earlier time, supports the conclusion that Van Gogh became interested in Japanese art in 1886.

Choice B: If Van Gogh had been interested in Japanese art prior to 1886, then it is very likely that at least some of the hundreds of sketches he drew between the start of his art career and 1885 would have been reminiscent of Japanese work. Since this is not the case, the art historians' conclusion seems justified.

Choice C: The fact that Paris was home to a unique market for a type of Japanese print supports the idea that Van Gogh became interested in Japanese art when he settled in Paris in 1886.

Choice E: Using a traditional Japanese instrument to create art as of 1886 suggests that Van Gogh became interested in Japanese art at that time.

Choice D is correct.