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: Medicine
Ptosis may be caused by a lesion of the: 
Select and explain. 
A. Oculomotor nerve, B. Superior oblique, C. Trigeminal nerve, D. Trochlear nerve
A: Oculomotor nerve
Answer: A: Oculomotor nerve 
Explanation: None