This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head & Neck, Subject name: Pathology
A 2-year-old girl was withdrawn from a day care center for excessive irritability On physical examination, she has multiple, small superficial ulcers of the oral mucosa. The ulcerations heal spontaneously over the next 5 days. Which of the following is the most likely diagnosis? 
Select and explain. 
A. Aphthous stomatitis, B. Candidiasis, C. Gingivitis, D. Ludwig angina
A: Aphthous stomatitis
Answer: A: Aphthous stomatitis 
Explanation: Aphthous stomatitis describes a common disease that is characterized by painful, recurrent, solitary or multiple, small ulcers of the oral mucosa. The causative agent is unknown. Microscopically, the lesion consists of a shallow ulcer covered by a fibrinopurulent exudate. Candidiasis (choice B) features white plaques.Diagnosis: Aphthous stomatitis