This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Opioids, Subject name: Pharmacology
The effect of morphine which has least tolerance is? 
Select and explain. 
A. Analgesia, B. Respiratory depression, C. Constipation, D. Bradycardia
C: Constipation
Answer: C: Constipation 
Explanation: ANSWER: (C) ConstipationREF: KDT 6th edition page 457Tolerance is exhibited to all actions except meiosis and constipation