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: Physiology
Preganglionic parasympathetic fibers are: 
Select and explain. 
A. Somatic only, B. Parasympathetic, C. Sympathetic, D. Cholinergic
D: Cholinergic
Answer: D: Cholinergic 
Explanation: None