This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Substance abuse, Subject name: Psychiatry
Withdrawal of which of the following causes piloerection 
Select and explain. 
A. Morphine, B. Cannabis, C. Smoking, D. Alcohol
A: Morphine
Answer: A: Morphine 
Explanation: Opioid withdrawal: The characteristic symptoms include lacri mation, rhinorrhoea, pupillary dilation, sweating, diarrhoea, yawning, tachycardia, mild hyper tension, insomnia, raised body temperature, muscle cramps, generalised bodyache, severe anxiety, piloerection, nausea, vomiting and anorexia. Ref: Ahuja Sho textbook of psychiatry by Niraj Ahuja 7th edition, page 43.