Ans. is 'a' ie. Submucous oral fibrosis " Submucous oral fibrosis is a progressive ds. in which fibrous bands form beneath the oral mucosa. These bands progressively contract so that ultimately mouth opening is severly limited. Tongue movements may also be limited. This conditon is almost entirely confined to Asians. Histologically it is characterized by juxtaepithelial fibrosis with atrophy or hyperplasia of the overlying epithelium which also shows areas of epithelial dysplasias. The etiology is abscure. Hypersensitivity to chilli ; betel nut, tobacco and vitamin deficiencies have been implicated. The scar bands of submucous fibrosis, which result in difficulty in opening can be treated either by intralesional injection of steroids or by surgical excision and grafting, but this has little effect in preventing the onset of squamous cell Ca in the generally atrophic oral mucosa (Submucous oral fibrosis is a precancerous conditon for squamons cell Ca)."- Bailey & Love