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: Biochemistry
Acetylcholine is the neurotransmitter in the cholinergic neurons. What is the precursor that acetylcholine is derived from? 
Select and explain. 
A. Dicholine, B. Tyrosine, C. Cholic acid, D. Choline
D: Choline
Answer: D: Choline 
Explanation: The conversion of choline by CAT (choline acetyltransferase) is responsible for conveing choline to acetylcholine. Likewise, the conversion of acetylcholine back to choline is by ACH-ase (acetylcholine esterase). CAT ACh-ase Choline ----> Acetylcholine ----------> Choline