The correct answer is: D. no article
The word “brother” is a common noun, which means it does not have a specific reference. In other words, there are many brothers in the world, and we cannot identify which brother is being referred to without more information. Therefore, we do not need to use an article before the word “brother” in this sentence.
The other options are incorrect because they all use articles. An article is a word that is used to modify a noun. The three types of articles are “a”, “an”, and “the”. “A” and “an” are indefinite articles, which means they are used to refer to a general or unspecified noun. “The” is a definite article, which means it is used to refer to a specific noun.
In this sentence, we do not need to use an article because we are not referring to a specific brother. We are simply saying that the speaker has a brother. Therefore, the correct answer is “no article”.