This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: ENT
All are precancerous lesions of oral cavity except - 
Select and explain. 
A. Leukoplakia, B. Erythroplakia, C. Diffuse oral submucous fibrosis, D. Diffuse aphthous ulcers
D: Diffuse aphthous ulcers
Answer: D: Diffuse aphthous ulcers 
Explanation: Lesions with an increased risk of malignancy

Premalignant condition : - Leukoplakia, Erythroplakia, Speckled erythroplakia, chronic hyperplastic, candidiasis.
Conditions increasing risk : - Oral submucous fibrosis, syphilitic glossitis, sideropenic dysphagia (Paterson Kelly syndrome).
The risk is doubtful: - Oral lichen planus, DLE, Dyskeratosis congenita.