This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Intravenous Anesthetic Agents, Subject name: Anaesthesia
Wooden chest rigidity is seen with 
Select and explain. 
A. Morphine, B. Fentanyl, C. Remifentanyl, D. Pentazocine
B: Fentanyl
Answer: B: Fentanyl 
Explanation: Fentanyl induced chest wall rigidity seen with high bolus dose of fentanyl. CWR related to opiate administration was first described by Hamilton and Cullen in 1953 . Following opiate administration, clinicians may observe significant difficulty with mask ventilation, respiratory arrest, and a rigid chest wall; this phenomenon has been noted with various opioid substances. The majority of repoed cases and physiologic studies focus on CWR occurring with high opioid doses --administeredas pa of anesthetic induction