Answer choice A states that the argument is flawed because it "ignores the fact that there can be general agreement that something is the case without its being the case." Ultimately, A is incorrect because the gallery owner does not ignore this. Even though the owner states "experts agree that in his later life Van Gogh invariably used just such broad brushstrokes and distinctive combinations of color," the owner prefaces this statement by saying "we cannot guarantee that he painted it." He also uses the phrase "VIRTUALLY certain." This shows that the gallery owner acknowledges that general agreement does not necessarily guarantee truth.
I hope this helps to clarify. Please reach out with any additional questions!
