Answer: C
K13.3 is the correct answer here as it codes for hairy leukoplakia. Oral hairy leukoplakia is seen on the tongue as a white hairy or corrugated passage. Most commonly, it is associated with HIV infection.
Option A is not correct. K13.21 codes for leukoplakia for oral mucosa that includes tongue but for hairy leukoplakia, code K13.3 is used. It is excluded in K 13.21.
Option B is not correct because K 13.1 codes for cheek and lip biting, which are not the diagnosis here.
Option D is incorrect because K 13.79, including focal oral mucinosis.