This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Human Immunodeficiency Virus, Subject name: Microbiology
[{'content': 'In a patient having HIV infections, oral ulcer is most commonly due to: \nSelect and explain. \nA. Candida, B. Cryptococcosis, C. Histoplasma, D. Trichophyton', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Candida (Ref: Harrison, 18th/e, p. 1549, 1550; 17th/e, p. 1174)* Amongst the given options, only Candida causes oral lesion in AIDS patient.", 'role': 'assistant'}]