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 the following can cause mouth ulcers except ? 
Select and explain. 
A. Sickle cell anemia, B. Lichen planus, C. Mouth washes, D. Psoriasis
D: Psoriasis
Answer: D: Psoriasis 
Explanation: Ans. is 'd' i.e., Psoriasis(lRef Dhingra &/e p. 217)