The correct answer is: D. no article, no article
The reason is that the word "rich" is an adjective, and adjectives do not take articles. The word "poor" is also an adjective, and adjectives do not take articles.
The other options are incorrect because they use articles. The article "the" is used to refer to specific people or things. The article "an" is used to refer to general people or things. The article "a" is used to refer to people or things that are not specific or general.
In this case, the rich and the poor are not specific or general people or things. They are simply people who are rich and people who are poor. Therefore, the articles "the," "an," and "a" are not necessary.
