The correct answer is: D. no article
Ankara is the capital of Turkey. It is the second most populous city in Turkey, after Istanbul. Ankara is located at the center of Anatolia, the Asian part of Turkey. It is a major economic and cultural center.
The word “capital” can be used with or without an article. When used with an article, it refers to a specific capital city. For example, “The capital of Turkey is Ankara.” When used without an article, it refers to any capital city. For example, “Ankara is the capital of Turkey.”
In the sentence “Ankara is the capital of Turkey,” the word “capital” is used without an article. This is because the sentence is not referring to a specific capital city, but to any capital city. The sentence could be rephrased as “Ankara is a capital city.”
The other options are incorrect because they are all articles. An article is a word that is used before a noun to indicate whether the noun is specific or general. The articles “a” and “an” are used before singular nouns that begin with a consonant sound. The article “the” is used before singular nouns that begin with a vowel sound or a consonant sound that is pronounced as a vowel.