A 60-year-old man has been treated for a t2nom osquamous cell carcinoma by radical radiotherapy. He has a history of chronic alcoholism and was a heavy smoker. Six years after treatment

A 60-year-old man has been treated for a t2nom osquamous cell carcinoma by radical radiotherapy. He has a history of chronic alcoholism and was a heavy smoker. Six years after treatment, he develops a painful ulcer in the alveolar mucosa in the treated area following minor trauma. His pain worsens and the bone became progressively exposed. He is treated by a partial mandibular resection with graft. The diagnosis is
a. Acute osteomylitis
b. Gerre,s osteomylitis
c. Osteoradionecrosis***
d. Chronic osteomylitis