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: Ophthalmology
An otherwise healthy person who wears contact lenses develops a small ulceration of eye. What is the cause – 
Select and explain. 
A. Acanthamoeba, B. Cytomegalovirus, C. Toxocarna, D. Toxoplasma
A: Acanthamoeba
Answer: A: Acanthamoeba 
Explanation: None