The correct option is C a, the
Option C is correct because both (a, the) are articles, the definite article 'the' modifies 'air' and the indefinite article 'a' modifies 'bird'. Option A is incorrect because both the words are nouns. In option B, 'a' is correct but 'in' is a preposition, hence option B is incorrect. Option D is incorrect because the first word is a verb and the second is a preposition.