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: Pharmacology
Sudden withdrawal of which of the following drugs could result in serious adverse cardiovascular changes in a patient taking the drug over a long time: 
Select and explain. 
A. Phenelzine (MAO inhibitor), B. Enalapril (ACE inhibitor), C. Clonidine (α2 agonist), D. Fluoxetine (serotonin reuptake inhibitor)
C: Clonidine (α2 agonist)
Answer: C: Clonidine (α2 agonist) 
Explanation: None