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
The effect of morphine which has least tolerance is ? 
Select and explain. 
A. Analgesis, B. Respiratory depression, C. Constipation, D. Bradycardia
C: Constipation
Answer: C: Constipation 
Explanation: None